Ryan,

Most varios I know use one of the techniques you mention for
switching.

I think you'll find a lot of experienced pilots essentially ignore
cruise mode by putting a wide dead band on the audio. The view is that
chasing the speed director creates drag more than it optimizes cruise
speed. I generally change cruise speed only for extreme sink. Also I
tend to try to climb straight ahead, even if the lift is a bit below
my McCready setting (again, most experienced pilots I know fly slower
than the speed indicated by McCready theory for a host of reasons).

Given all that I'd set my vario to switch to climb based on airspeed,
and a pretty high one at that. My concern with your suggestion is that
you might get a lot of spurious switching to climb with gusts or
thermals you don't intend to climb in unless you put a time lag on it
- which would create other problems.

9B