An in-between solution is the external mixer. After sliding trays but before computer radios you could buy an electronic mixer that plugged into the servo leads to mix elevators and ailerons. My last delta wing, a Balsa USA Force One was designed to use a central elevator and ailerons on the wing tips but was modified to use two control surfaces as elevons with computer mixing in the radio. I hadn't installed the pushrods yet but you can see the control surfaces on the trailing edge of the wing.