I'm not too interested in having MKX again only with 50 Characters. That's a lot of system tearout when the whole idea is having a roster like this rumored MK made possible because of reusing assets from MK11.
-Don't Introduce Breaker unless you plan to add a third bar of meter. You would also have to rebalance the current armor breakers that are good to still be useful in your new Breaker world. If you can't do all that work in a base roster of 50, don't bother with Breakers. My personal opinion is both systems suck in different ways and can sometimes benefit the opponent when they're the ones who got hit. You should eat the combo.
-So Instead keep breakaway but scrap the useless armor breakers among the cast for good ones like Kabal, Baraka, Kollector, Kano. Everyone should have breakers that don't just make you think twice about breaking but FEAR the idea of eating more damage on top of having no meter left. How many times did we see people respect Kabal's combos at CEO simply because they didn't want to eat the KB and lose the game?
-I'm not interested in Run coming back, but some characters in 11 being faster than others is a total crock, Everyone not leaping all over the place like Jacqui, Kabal and occasionally Kitana should have the same movement Kotal, Mileena, Rain and Fujin get to have. Making it a standard across the board makes the overall game faster.
-I'd keep the automatic meter. I don't care about your meter build dreams in a game with 2 bars of meter over 3, I'm sorry but I don't.
-Remove wakeup u2s (keep them as flawless block attacks), keep wakeup u3s but do something about forward roll... perhaps have throw KBs work on getting grabbed out of your roll? I dunno but you need to have something to put fear in players who will easily roll their way out of a bad situation.
-Fix the slowdown of the Finish Him screen, this is a minor issue but it kills the ability to end the match on a swaggy combo ending in brutality
So yeah that's how I'd go about it. And while I think the idea of making it MKX but hueg roster is pretty disastrous, I'd still happily take it over any Injustice 3.