The only thing missing from their list in these open world games is the superhero type, outside of that they've done damn near everything.
The day they decide to make an Open world style zombie game it's a wrap for everyone even thinking of making these shyts.
the closest thing was crack down. that power up system in an open world sanbox was beaaaauuuutiful when it first dropped. now crackdown 2 wasnt even close on the fun meter. they tried to do the zombies thing with a twist. it wasnt good. to many zombie games.
crack down is where you Earned super human strength, weapons ability, driving ability. kicking fools across the street. throwing cars at people. "POWER UP". blasting the boss in the sky then shooting him one more time with a grenade launcher to juggling him in the air a little longer just for kicks.
insane.
Now like you said, if they ever did say an Injustice God among us game where its open world. then have an online version similar to DC online where you can create your own character and mix/match super powers while gaining others. all in the same open world format with a tight story line. it might be the greatest game ever made. but make sure the open world isnt some fake city like a crackdown. naw put them super heros in Los Santos, Liberty City, miami, etc. So if i got some superman like character, if i so well choose. i can pick up capital records building and throw it in the pacific ocean.