Like others have suggested, have the ability to change the wings thickness/show the actual airfoil, but along with that also be able to change control surfaces independently from the wings shape, as well as add true flaps, and the option to have more than one connection point for the wing so that larger/faster planes can handle heavier payloads/higher g-forces without the wing physics breaking. Another addition could also be the incorporation of fully customizable engines such as in SimpleRockets 2. One final addition could perhaps be to add in vector thrusting nozzles and fly-by-wire. Would be happy to see any of these in game but I perfectly understand if it can’t be.