The bit I can't get my head around, is the forces in the turn. The Super Cub at ZERO groundspeed has NO momentum to overcome. Here centrifugal/centripetal forces don't apply. Therefore, with the aircraft banked, the horizontal component of the total reaction is unbalanced!!!
First, as soon as the airplane starts the turn, groundspeed will change. But that doesn't matter anyhow...
Also, if it has 0 momentum, why does it need power to remain aloft and maintain that "0" momentum? It is because there are external forces acting on it from the airflow.
If you are above a smooth cloud deck and do not have GPS, INS, or DME, you do not know your ground speed, nor does that ground speed affect your flight condition. The airplane also does not know or care about its ground speed -- regardless of cloud cover -- because it can only "see" the air around it. When aloft, the airplane's frame of reference is the packet of air surrounding it -- NOTHING else. All forces on the airplane are with reference to that air packet.
If the earth happens to pull a mountain or building in front of the airplane, that's a whole different story, because the airplane will not be aloft for long...