Much more takedowns. Like if you're in front of a guy, you can take him out. The takedown would be something like, Batman kicks thug in stomach, jumps over his back, and then does a silent takedown. That would be cool. And also, maybe if you tap Y and a different direction on the analog stick, you would do a different takedown? Just tapping Y would do a standard silent takedown. Y and right would have Batman do that thing where you chop the person on the shoulder and they fall back (I don't know if that really works). Y and left would have Batman violently turn the thug around, thug flinches, Batman punches in face. You get the point - more variety.
Also, I would like to move unconsious thugs. You can let set them somewhere where it attracts his buddies, then jump down and beat them all up or something. And no suicide collars, please.