RE: one battery system possible
Negy,
Imagine what would happen if the battery is drained by the ignition system....
If a separate on-board radio battery still has some juice in it, you could make a dead-stick landing, but if it is the same battery???
I would strongly advise against it.
Even electric power models that do use a single power source, have a BEC that reduces, or cuts off engine power, but retains control of the model...