I'm actually very concerned about what Injustice 2 might turn out like. I feel like the first game was a really good game for a new FG, but I'm mostly concerned because of how much more I ended up liking MKX. MKX has just has a lot of things that would work really well in Injustice but may be viewed as MK mechanics and not universal ones. The variation system being the biggest thing I would like to see folded in.
Variations brought a lot of things to the table in terms of people being able to find a strain of a character they like that suits them, or having characters have good odds at having viable variation. That and just giving people a more realistic way to be a character loyalist with less likelihood of boxing them into bad match ups. They also make sense with the Injustice lore having smooshed together actual character variations at the story level. I don't think 3 variations are necessary, but two makes a lot of sense. Not just for I2, but for fighting games in general.
I think the continued integration of level intractables makes sense for the game, but I think they need to operate a bit more like MKX. There was a bit too much of it in Injustice for my tastes. With that said I do think the level transitions are cool, and fit the superhero identity of the game. Those can stay in.
I really think the clash system thing needs to go. Just do a basic combo breaker and let that be the end of it. None of this momentum killing, dramatic sequence business. I never even bothered to learn how to initiate a clash because I hated seeing them so much I wouldn't have done one anyway.
I do like the idea of the unique character traits, but think the idea should be revisited if at all possible. Having only two formal attack buttons, one hybrid launcher / combo button, and one trait button that always does different things where four formal attack buttons are usually found, made the entry into Injustice more complicated than most fighters. The system works fine, it's just unique, and unique in a way I never got fully comfortable with.
I do want to see Batgirl again, but that's because I always want Batgirl around. I was never into the game enough to know she was supposed to be good/broken. I just like Batgirl. Overall I liked the character selection. I found it really hard to pick a character and wanted to play everyone. It would be nice if they were a bit bigger next time around.
I really hope Injustice 2 is in the middle of happening, and I hope it's as good for me as MKX has been. I like fighting in the DC world better than the MK world, but right now, MK just does the fighting part better. Fingers crossed.