What you want is Maverl vs Capcom (removing the Capcom characters) and put instead the Injustice characters.
I don't think this kind of game would exist (DC vs MARVEL) because neither of these company has a video-game section. they would have to use a third party company for make a game like that and that would be really difficult. for characters right claimers and whatever idk. there is always problems with this topic.
However, cosidering the posility a game like this could exist. It will be pretty interesting watching new playable characters far than the usual ones we are custom to see. Like when I watched Nova or Dormammu (both MARVEL characters that I had no Idea they existed).
You came across with a good idea.