Most Cox RTF were the proverbial rock on a string. Since they didn't have enough power to haul the plastic there isn't much hope of putting any rc in them and flying them either. Besides the aerodynamic of their wings would be terrible ,no airfoil and basically an undercambered piece or plastic..
Cox RTF, and Wen Mac,Comet,Auroura,K&B etc, did more to discourage youngsters from this hobby then any other form of available ready to fly planes. They looked wonderful but delivered very little in flying fun.
Besides you would need to get ailerons on them, bigger tail surfaces. And then just think of what some of those old Cox items are selling for. It's enough to make me cringe at the thought of crashing that much loot.