Even if it did break some scripts that required double evaluation, it would be very easy for the people writing/using such scripts to do a Replace All on "timer" with "timer -whatever_switch". Or, so you don't just replace everything without knowing what's going on, you can just fine each instance and replace them. I could do that in Invision, which is a fairly large script easily in under half an hour... probably under 10 minutes. That's far less intrusive than other changes that require a lot more time to make adjustments for.
I'd support this switch with it defaulting to single evaluation.
