RE: U-joint for motor mount instead of flaps?
I've seen 3D type planes that use thrust differential on twin engines to help turn the plane but I don't know of any that use a vectorable single engine. If you are suggesting using vectorable thrust instead of the normal flight controls, this would be fun to experiment with but I think I would try it on one of those indestructable foam planes first. What would be even cooler would be to couple a vectorable thrust control with the regular flight controls. A plane like that would be capable of some really bizarre manuevers.