it would be cool if you could have some sort of in game robot designer in which you could build a robot voxel by voxel or inversely carve one out of a chunky voxel base.

being able to create custom joint placements and body structures would be incredibly fun and it would also be incredibly wacky

(imagine sponge-bob taking on a mark 3 hammer bot!)
with this it would also make sense to add physics based voxels or soft-body voxels (i have no idea what im saying) in order to make things like capes or moving shoulder pads (like how the emperors pads bounce in the cutscenes)

they could also make things like capes, intricate designs, and more!
additionally, it could be interesting to give people the ability to add custom sounds.