If they couldn't have 8 Ice Climbers on the screen at once, they could have just made less than 8 colors for them. So if it could handle like 5 max then just give 5 colors. It's not ideal but it's certainly better than cutting an entire character or mode.
Anyways, if the 3DS version didn't exist then we would have the successor to Brawl that we should have. Every franchise would have at least one new stage (none of this "Earthbound and F-Zero, 2 franchises in the game since 64, have no new stages on the Wii U/Donkey Kong/Zelda/Pokemon/Wario/Kirby only have one new stage" nonsense). While we may not have gotten Smash Run, Smash Tour probably wouldn't have been the "main new mode". We might still have gotten it, sure, but it seems like it didn't take much work to make so we might have gotten an actual 1P mode.
Characters like Zelda/Sheik might have stayed as transformations, but then again Sakurai said there were other reasons too for them being split so maybe not. Pokemon Trainer as a whole might have come back though. The 2 DLC characters we know about (Mewtwo and Lucas) seem like they've been planned for awhile, and Sakurai definitely does not seem like the type of person to intentionally hold off game content until post-release to make it paid DLC, so maybe they (or at least Mewtwo) would have been in the base game. If Roy and Ryu are actually a thing, maybe they would have been the first two DLC characters.
The game might have come out a bit earlier, but I'd like to think it would have been released on the same date but they just used the extra development time to make the game better. And as for it being on the 3DS, they could have had a watered-down port of the Wii U version on the new 3DS released after the Wii U version was released (so basically what we have now), or like a port of Melee/64 or something.
And finally, we probably would have had a better name than "Super Smash Bros. for Wii U". My guess as to why they skipped using an actual subtitle this time was because they were worried people would get confused about the whole dual-system thing, and if each version had the same subtitle, or even different ones from one another, someone might have gotten the wrong version for their system. It sounds silly, yes, but I remember back when Animal Crossing New Leaf was announced, so many people kept asking if they could play it on their regular DS. And then there was that guy who somehow missed Nintendo's constant reminders to register Mewtwo on Club Nintendo, so I know for a fact that if Smash 4 had actual subtitles, someone would have bought the Wii U version for their 3DS and then would angrily claim that Nintendo wasn't "clear" in how they advertised their games.
tl;dr, it would be called "Super Smash Bros. Riot" or something, we'd have the Ice Climbers, probably Mewtwo on the base game, maybe Lucas, a better stage list, an actual 1P mode, maybe character transformations, and a straight-up port on the new 3DS in 2016 or something.
) and Smash Run and Smash Tour would be together.
