Please read this I know it's long but it will be good in the end it took me a few hours to make this and please comment on this if you really have something to say.

So it seems there is a rumor that we will be getting a Super Smash Bros. 4 Deluxe (or for Switch I guess) soon for the switch what I would like for them to do is merge both the Wii U and 3DS content to Switch version along with new content. They could at least bring back the Ice Climbers since the 3DS version was the reason they didn't come back since it was not as powerful than the Wii U and on there and maybe a couple other new characters and new stages.
www.heypoorplayer.com/2018/02/…

But also I have a small worry, because according to the well sourced Emily Rogers, Nintendo seems to be porting New Super Mario Bros. U + (Yup plus as U sounds kinda misleading for the Switch) for the Switch as a port (not sure what kind of port yet). I mean the original game was at least descent than NSMB2, but I certainly won't be buying a completely straight port of that game unless they do bits of changes and improvements which I do have some ideas. but TBH I rather have a Super Mario 3D World Port over New Super Mario Bros. U any day. I understand there making Wii U Ports because many people missed out on them back in the Wii U era and Nintendo seems to be porting Wii U games that have sold at least 5 million copies.

SOURCE: www.resetera.com/posts/3963908…

I don't hate New Super Mario Bros. U like I said better than NSMB2 they at least did some brand new things like.
Obviously this game has a different storyline, new enemies, new power-ups and features, and breath-taking graphics! If I have to explain what the storyline to every person saying it is the same, I'll do it. Bowser doesn't grab Princess Peach and goes to his castle, he punched all the others and left Peach with him and in her castle.

Here are my ideas what they could put it in if the port becomes true.

-Make Mario no longer be restricted to a Player 1 character, like in Super Mario 3D World.

-Each character with there own abilities and stats. Wouldn't change the gameplay too badly. Just requires more programming and animation.

-Mario is average.
-Luigi is a higher jumper, but has slippery tractions.
-Blue Toad runs faster but is a terrible jumper.
-Yellow Toad can throw objects farther and harder but is slow at running.

-Have New Super Luigi U included in the port. (It's going to be Luigi's 35 Anniversary after all this year)

-Brand new music tracks to replace the lazily recycled tracks. Even if there remixes to New Super Mario Bros. DS as those have unique music tracks.

-Better Graphics (the Wii U's version looked like plastic figures, even Super Mario Run did better for it's graphics, so maybe it could look similar to that game), so 1080p in dock and 480p on handheld mode.

-New Characters, Toadette as a brand new character, even if it breaks the Super Famicom color pattern (Because Mario, Luigi, Blue Toad and Yellow Toad represent the Super Famicom's colors on there logo and Wii and U). Nabbit still remains in New Super Luigi U replacing Mario. Yes I know it's another Toad but a unique one at least.

Toadette can spin jump and her pigtails will spin along with the twirl and she can hurt enemies (similar to the Raccoon/Tanooki tail spin minus hovering and the flying part and works much more effectively on the spin to not get you damaged easily) if she spin jumps towards them, her weakness however is that she can't throw items very well so yeah even worst then Mario's and the other casts throw physics. But stat wise plays like Mario.
www.mariowiki.com/images/4/41/… it's similar to this ability in Mario Super Sluggers but she doesn't spin on the ground and doesn't enlarge while doing that.

Maybe once you save Peach this time after beating the game, you can unlock her, she would be slow and can glide in the rumored port like in Super Mario Bros. 2. Since Super Mario Run finally got Peach's dress animated nicely. That is why Peach wasn't playable in New Super Mario Bros Wii and the original U because the developers had trouble animating her dress back then in those games engine, so hey technology advances hopefully. But if Peach comes to the final battle she can just simply save a Toad like in Super Mario Run or just takes you to the ending instantly. 

Miyamoto wanted Peach to be playable in New Super Mario Bros. Wii, But yeah the dress was the problem and honestly that is a bit of a pain to animate so I at least agree with him on this, until Super Mario Run attempted it pretty good, check it out here or see the qoute below, www.destructoid.com/peach-s-dr…

"Originally, I thought it would be nice if we could have Princess Peach in there as a playable character," he said through a translator, "but in fact, the Toad characters have a physical that's a little bit closer to Mario and Luigi. In particular, if we had one character out of the four that wore a dress, we would have to have special processing and programming to handle how the skirt is handled within the gameplay." So that fairly implies they would have to make a brand new model and animation. The Toads after all use Mario and Luigi's animation and it explains why they were in because of there body shape.

Now the same thing is explained again why she didn't appear in New Super Mario Bros. U and because the team was only using Mario's animations same reason why Toads were used again and it wouldn't be good for her to use Mario's animations. Your likely thinking yeah give her the sports outfit, no those are for the sports games and wouldn't fit theme of the main games very well, the spin-off games aren't canon, but I hope the port at least gives effort and gives them brand new animations to make them playable. So at the same time I feel they weren't trying. It's more forgiving in New Super Mario Bros. Wii though since it was only a newer start.
Toadette could at least use Mario's animations, but the pigtails are a different story. So it's possible they didn't have time to make custom animations for new characters, not enough time or money to get it done, not enough people to progress with the animation time or weren't trying to be creative we don't know. They could maybe fix it in the possible port. Animations for a individual character is quite a lot of work after all. 

The comment is in jest, but it holds some truth.

The Toads are more a similar size to the Mario Bros. than either Wario (too fat), Waluigi (too lanky) or Peach (all wrong). 

In a game like Super Mario Bros. 2 that might not have been so much of a problem given they all different attributes, and let's not forget that the Mario sprites were planted on top of the Doki Doki Panic's sprites. Of course Sprites are easier to make.

Here it would not have looked right, or would have had to alter and complicated the gameplay.

SOURCE: mynintendonews.com/2012/11/26/…

With that not only would we have a bit more original characters then just simple recolored Toads, but we would also have females as well (fan service! JK)! I will certainly like the port if one or both of them get included as playables in some way they can closely get in. Miyamoto created them and at least there original in design therefore not generic and boring. characters not created by him sadly won't make it, no thanks to his stupid restrictions since he is involved with the original game.

There are others but may not have the chances likely.

But before I start this is why Miis were playable in other modes. than new characters. So I guess they were bit easier to put in because they also share Mario's animations. 
mynintendonews.com/2012/09/12/…

“We did consider that when we looked at which characters we would use. We really came down on the side of using Mii characters rather than some of the characters you had mentioned. Through the technology of HD, you’re going to see more expression and emotion on the Mii character faces. Of course, we’re going to continue making Mario games, so you can maybe look forward to some of the things you were asking about in the future.”



Toad (himself) - He could possibly replace Blue Toad himself but the problem is that the Mini-Game houses have Toad species that has his actual characters appearance, unless the colored Toads take over the houses. (Like Red and Green Toads in those colored houses). That Toad is a little bit unique at least, but then it would be strange to have Yellow Toad as the only generic one with you. Unless Yellow Toad gets replaced some how. He would just work the same as Blue Toad above otherwise.

Daisy - It would be rather awkward for her to save Peach with the others, even in New Super Luigi U adventuring with her love interest Luigi to also save Peach along with her kissing Luigi in front of Daisy. in Super Mario Run if Daisy beats Bowser, Mario still saves Peach and get the kiss. Like it would be even more strange if Peach kissed Daisy especially there both human. For Toadette that is kind of different because she is not human like her species and the kiss is just a thanks anyways. She would make a good Yellow Toad replacement however though. Of course she could be slow and be a double jumper like in Super Mario Run.

Wario - He could somewhat appear the closest, it wouldn't be a problem if he just plays exactly like Mario. But his animations are different so he also wouldn't work very easily then we think. He could of course replace Yellow Toad, but if the characters have there own stats I'd be a little worried because the characters build have to make sense for there body size and stats. Wario was kind of a problem in Super Mario 64 DS because he was very slow and a really horrible jumper but just good in strength. But he could at least have his classic shoulder bash move back which would at least make him go faster, something Super Mario 64 DS was missing, it worked fine in Wario World for the Gamecube since that game came first and uses some of his voice clips but lower quality.

However Miyamoto made an interview to explain why Wario was not playable and honestly it was a really bad response. Because this is why.

"Mario and Luigi are the same as always, of course, and suggestions for the other two characters included Wario and Waluigi, Toad, and Princess Peach. The thing is that with Wario he'd need to have a fart attack, Peach would have to be able to fly with her skirt, and so on. With this game we wanted every character to play the same way."
SOURCE: www.cubed3.com/news/13349/1/mi…

Honestly I really hope he is joking (though he could be by the sounds of it) because why would he need to fart in order to be playable? The other characters play all the same. Maybe unless the characters have there own stats but honestly a fart really? Why not the shoulder bash? Oh right Miyamoto doesn't do the Wario games and of course didn't create him it's even to the fact he amusingly never knew Wario was in Super Mario 64 DS. So of course he doesn't know who he is by much, Wario only farts in Strikers Charged and the Smash games.
It's no wonder Wario is used in the spin-off games now, he always has to dislike on creative characters not created by him same thing to Rosalina, it just really shows he is jealous and such a simplistic person thinking everything works for him his way.

He always has to make stupid excesses why Wario can't be in the main games when he started as one, The interview was in 2009 so it's certainly old yes. 

So minor things here...

Waluigi - Certainly won't work out at all he is just a spin-off character plus he is way too tall for some of the levels design and he has his own animations anyways.

Rosalina -  She never really appears in the 2D games, and not to mention it would be way too random to put her in for how her character goes, it was already enough that she appeared out of no where in Super Mario 3D World, sure she can just simply spin jump and run slower, but at the same time it would be odd putting her in a 2D game even more than a 3D game since she is more connected in 3D titles since Galaxy. It would also be weird if Peach even kissed Rosalina as well.

-Multiplayer Changes to make it less chaotic. 4 Players kinda get in the way a bit. With crowded levels and by getting jumped on a lot.

-Baby Yoshis should not be taken to levels and like the Glowing ones they should reward you a 1up for letting it survive towards the Goal Pole, they are too over powered. It also seems a bit strange even for the fact that ridable adult Yoshis cannot be taken to levels and there not as overpowered. In fact bring back the Baby Yoshi Eggs that appeared in the E3 Trailer, there still in the games files still functioning great, it was really odd that only the Glowing Baby Yoshis have eggs while Bubble (Blue) and Balloon (Magenta) Baby Yoshi didn't, yet there were merchandises of there eggs and also making cameos in Nabbit's House in the background. I think it was really stupid putting the Baby Yoshis on the map at the last minute of release. It made the game way too easy with them being brought to most levels.
www.wiisworld.com/images/news/…

-Amiibo Support? (Since amiibos weren't made by that time yet in the Wii U era)

-Replace Boost Mode with something else, since the gamepad for the Wii U version is used for that mode. As the gamepad for switch is for handheld mode only.

-Add a Hard mode, where you could either die no matter what power up you have or like in Super Mario Bros. 1 and Super Mario World you revert all the way to small even if you have like a Fire Flower or a Super Acorn.

-A new world after Superstar World?