Single Part Gimbal Mount.

A gimbal mount like what you see on the rocket engines, just with an attachment point, Bottom and Bottom Shell. Could be used in a few ways like making custom rocket engines or having TVC with a jet engine. This is already achievable in the game as it currently is, but they are finicky and don't work all the time. For mostly this reason I think it would be a rather neat addition to have a custom gimbal mount you can attach to parts to.