Add Rotator/Hinge Stabilizers
Rotators and hinges are incredibly floppy when you add just a teensy bit too much weight onto them, making large creations with moving parts either required to be slow, or way too bouncy.
A stabilizing function would probably be wonderful for the people who make ships, tanks, or aircraft with independent guns. Especially if there was a "point-to-cursor" function.
Maybe a few forms of stabilization? A standard "sticky" stability that eliminates bounce, an "independence" stability that points to where you keep it, and a "cursor-guided" stability like a turret.
This would open up a whole range of creation options, from gunship aircraft, to surface-based vehicles with more dynamic controls. Creations get complex and control-intensive fast.
Might even be able to add some levels or missions to the game with it, like a gunship or AA level. Something like shooting down drones.
This would add a huge range of options, please consider this.