Well, it seems Ive been suicidal for a long time then.

Power failure? If the plane goes thru a power failure, cutting the engine would be the least of your worries. If the ignition system has a power failure, you already have a dead stick in your hands.
I have seen my fair share of mis-used opti-kill stuff, and alot of optic-killed engines by mistake, because ones fingers unintentionally touched the "kill switch" - normal cut-off wouldnt kill the engine if its above idle. So unintentional pressing would save your plane from having an unexpected deadstick. Ive been flying planes for a long time, never needed opti-kill. For me, Its just another thing that could fail. (just like a power expander)

The simpler, the better.. (IMHO)