just the editor. Build your own armor, build your own gun / melee weapon from blocks. It could be exactly like the ship editor, even using exactly the same blocks, only scaled down to 1/10th size. (shields, power gen, armor plating, even thrusters for jetpacking.) New blocks for the new features.
To make the armor work, we would need a more anatomically correct player character, with distinct areas where distinct armor segments could be built upon. (Head, torso, groin, etc.)