MKX was a little too divisive to be the base for a legacy game imo.. Most casuals dont know/care what a legacy game actually equates too (in my opinion.. I certainly have no data to back that up) and since the competitive crowd has been pretty divided.. I just dont see the appeal in legacy.
Sure, cost/dev time/effort can be a factor but if the whole thing has to be picked up and dropped into a new engine, along with tweaks, changes etc, I dont see the time and effort saved as being very much, all said and done. I guess mocap data would be transferable and that has to cost a small fortune to get.. but I dunno.
If I was to craft the perfect MK, be it vDC or X1, I'd take a gear system like Inj2 has - from a competitive play standpoint I want the damn cosmetics. Sorry, but thats just an amazingly dope idea and I love it. Then I'd take its extra ability system, but abilities wouldnt be tied to levels or gear or unlocks, they'd just be available. Every character would have a base set with 2 open slots and a pool of 4-6 extra abilities to choose from. All abilities would be implemented and balanced for tournament play. This would allow SO MUCH freedom. You could very much make a character your own and tailor that character to how you want to play and what you're comfortable with. Additionally, it would allow characters to tailor themselves to their opponents and help to prevent heavily lopsided matchups. This is under the assumption that functional balance is maintained of course. A smart and slick UI system would need to be in place as well to ensure that choosing abilities and such in tournament was extremely fast and trouble free. Once those systems were set, you build the game around MKX's view and sound design. I feel like the execution and general skill floor should be right around where MKX's was, but the Inj model would be fine as well. I personally like the wake-up options in Inj in terms of delay and extra delay, roll, quick rise, etc.
Game play wise, I'd like to see a great mix of footsie/spacing/pace characters, rushdown characters, trap/setup characters and zoners with the usual hybrids spread around.. The ability system would be amazing in this regard. I like powerful offense and usually favor balancing around characters having very strong tools. Even if a character is balanced, no one wants to play a boring, vanilla feeling character. Everyone wants to have fun and powerful shit to do. Outside of fringe characters designed to have exceptionally strong or weak defense, defensive tools should be largely universal IMO. As always some characters are going to have strong wakeup stuff and some wont, but the bulk of defensive options should be part of a universal system. This allows offense to be stronger as a whole, but keeps it from being oppressive and obnoxious. I want to see zoners, but pewpew zoning needs to be looked at before being implemented. Its not fun to fight against, even if you can fight against it successfully. Its not fun to deal with even when its balanced... Obviously in a competitive game, not every tiny second of a fight can be "fun".. but I think adding things in that are actively fun killing for one side is just a bad idea. BY ALL MEANS keep zoning and make it powerful, but make it more intuitive and involved. Hood, Darkseid, Harley and Ivy are examples of zoners that I find interesting to play against.
Shrug, that's my take on matters anway.