Ability to edit props
It would be wonderful if we could edit props the same way we can edit scenes. For example, when I overlay a pair of glasses on a character, the "arm" of the glasses that would be behind the character's head shows up across his face. If I could erase that arm, it would appear proper. The same goes with just about any prop that a character might be holding (such as a guitar) where you'd want to see the character's hand or arm.