I'd be happy with a rehash of JC2 in terms of vibe, but with balls to the wall physics/interactions and all the modern bells and whistles.
Even though the mechanics expanded a lot in JC3 there was a distinct tone to JC2 that's still unmatched, it even had a great atmosphere from the world all the way down to the incidental music/fx. The character design was better and the world felt better designed as well as having a great degree of variety. I remember playing the demo on PS3 over and over.
As for JC4, I checked out after a few hours, it just felt and looked awful.