RE: Official Hobby Zone
The supercub that comes with a 2.4 gig transmitter (Supercub DSM, I think it is) has the option of adding ailerons. I think that it has a combined ESC/RX, but it does have aileron output. And by the time someone is ready to add ailerons, they probably have enough experience doing repairs that the mod will be easy.
I agree that the basic supercub (with the 5 wire servos and the RX/brushed ESC) is tough to upgrade and probably not the best choice (especially since it's alos 27 MHz and more vulnerable to interference)... but then again all you have to do is pull out those electronics and install a new RX and servos (and cut the ailerons into the wings and install those servos) when you're ready to move to the next step.