We're talking 2.4, right?
Guys now running with a battery pack for the receiver and a second for the ignition already have 2 switches? If the plane is big enough to carry that setup, and you think it might have enough left over to carry an opti switch, you can add that, do some simple rewiring, and have redundant power, along with twice the available amperage to your receiver and servos? There's no downside to that, and the cost is the price and weight of the opti switch - which is an excellent plan anyway.... pretty easy to justify?

IMHO, the only better setup in planes up through 30-36cc might be a single A123 battery, but that's just me.