Soft Body Vehicle Physics
Stuff like this, hopefully.
I know that he was definitely a polarizing figure but Heedicalking brought up a good point that a lot more of what's in the engine could be brought out to awesome effect. There's a lot of Torque features that don't function in Blockland that would really increase the capabilities of modders. There definitely is a lot that can still be done already, but when it comes to adding things in like hovercrafts it just blows up even further from there.