Some admin tool that would make it possible to connect two entities by parenting/welding (a bit like gmod) would be fun to play with.

For use with the telekinesis plugin where you can move objects in all directions and rotations but then connect these two objects for instance attach lights etc to a vehicle.

Basicly some Gmod features in Rust.

I have been playing around with attaching pianos to vehicles, Unity does not play along with it.