I'd like to see Solana and Bogon back again, Gadgetron, Megacorp. And also, I really liked the graphics style they had in ToD. Also, there should be more inventive gadgets(I mean like how many times did we actually use those heli-pods? 3 times). And clank sequences should be replayable.
I also kinda liked the omega-mods from gladiator(deadlocked) and the constructo-weapons. And I'd also like to see the crystal/souls/moonstone sections back like in Going Commando