I have some of the same issues in Utah. I live in the mountains at 6700' but often play 1/2 hour away in Salt Lake at 4200' so I also have significant pressure changes... add in temperature and humidity and it can be a problem. I always try to get to the gig with enough time for my guitars to equalize temperature but can't always do it. I've been in a dust storm in Phx once, too... it was like being in hot dry fog. Glad I wasn't gigging.
Anyway, I played one of the new Peavey's equipped with the auto-tune system today. I have to say, I liked it. I think the thing it does that the others (Variax and the re-introduced Roland VG Strat, which btw sounds sweet) don't do, is that if a Variax or VG is a bit out of tune, when you switch to another tuning it's still out by that amount. Or do the Variax/VG actually do the auto-tune thing and compensate for your strings being out? The rep said they don't but I'm not sure...
This one wasn't connected to midi so I wasn't able to quickly switch to alternate tunings. But what you can do, is for example if you want Baritone tuning, you bar across the 5th fret and engage the auto-tune function. The tuner compensates by making the 5th fret regular EADGBE, so your open tuning is now Baritone. Or if you want Drop-D, you just grab the low F# and hit auto-tune, it makes that 2nd fret note into E, which makes the open string D. Pretty cool. I'll be interested to see the full-featured product.
Mesa, did you get a chance to try it out?