Splitting hairs here. Not sure how important this is. If things get bad enough for your fail safe settings to be enabled when on 2.4, not sure how important it is for your engine to remain idling in any case.
Regarding fail safe settings taking precedence over the opti switch programming, in the case of low voltage or signal loss, how is the receiver going to maintain the voltage or signal required by the opti switch? The receiver is not able to boost voltage or generate signal that it is not receiving.
Even if the receiver is able to set a pulse width/generate a signal that will keep the opti switch running (not very likely in my estimation) thinking it would be impossible to trick the opti switch in low voltage scenarios.