RE: Running CDI from RX
Yep. At least with my models. However, if my ignition goes nuts I'll still be able to land the plane since the rest of the radio would be working fine. I don't need a running engine to land.
My professional stuff has multiple power (and comm) redundancies on both ends of the tx/rx circuit, including self power generation. Your not bantering with some amature, inexperienced modeler.