Adding yaw control would make planes much more maneuverable and realistic, while remaining true to simple concept.

As for Contraption:
Some players utilizing the simple-planes, little-logistic and create made a movable large aerial craft


They seated a contraption-ed barge from little logistic on simple plane helicopter. That looks really great, better if we can bypass the involvement of little logistic, and have a way to control that pseudo-airship from a place with better view.

Quadrotor drones with remote control, video streaming(any way to see with drones' eye) would be a fun thing to play with.