The reason why jump doesnt help is because although there are z axis co-ordinates, there is no way for the character to impliment the Z axis. IF you could not only does that open up the ability to jump onto things, you could also swim up or down.
However i think its impossible to implement it into the game now.
Jump has always been in game, even pre cu. I remember binding it to space, before i realised that it did nothing and there was more than a bit of chatting in game :P
my greates pet pieve about galaxies, I cant jump over a two foot high box, but i can run up the sides of giant cliffs!