First of all, MK11 is best in the franchise to me in terms of graphics, characters' looks, depth and roster. That being said, with a few tweaks and one big change I think we could have the best fighting game in history of all fighting games:
1. Modify variation system - I think we're too far gone to rewind this feature and while for some characters it works as you can really make them unique and the moves are actually great replacements that would be hard to implement otherwise, there's too many characters were the variation options are very limited or are very weak to take a slot. I think scaling it back to two with each one meaning totally different play styles that are just set and not customisable, but very deep would be an option.
2. No customisation - I appreciate the effort in MK11 by NRS, but I doubt it's about giving fans what they want and rather a way to get us to spend money. The random colour combo's, the lack of diversity, not just giving us MK2/3 skin for the ninjas but have us grind to get the right combination, (false) advertisement of skins in trailers - from the first of Scorpion in MK3 outfit and MK2 mask to Terminator's iconic look - it just feels all around cheap. This would also eliminate the constant requests for skins and make it all about now, not trying to relive the old days. It's time to let go for at least one game.
3. Zoom out again - we are close to the action, which has its advantages but it's one of my main gripes with NRS' choice with regards to fights backgrounds. Most arenas, even the outdoors ones feel very enclosed and I love stages where you can get a sense of where you are, a sense of depth. If they stay in the current format, then I'd say zoom out for certain arenas and keep it close for others. For example: Dragon Grotto, the Fight Club, Tarkatan War Kamp (has depth and doesn't feel closed off) or Hideout stage zoomed out wouldn't change anything, but think about Koliseum, Sea of Blood or Fire Garden and its surroundings.
If they decide to keep it close, then I'd suggest taking it to the next step:
BIG CHANGE:
Cinematic fighting - shoot the fights with several cameras in 3D close, far away and from all possible angles to make it feasible and then have a cinematic mode and or have us choose which camera we prefer. This would give us the closest to a 3D experience without the fighting actually being full on 3D. While sidestepping would be silly, I would love a dodge option. This would also make the arenas much more immersive and the whole fighting a much more intense experience.