You can put a spacer in the air spring to reduce it permanently by 20mm (or any amount if you want to make a spacer). It's a very quick job.
You can buy an air u-turn cartrdige but it will be pricey.
Personally I don't find the u-turn system good for on the fly changes. I tend to wind down my Lyriks to about 140 and leave them in one position. I think it's something like 7mm per turn of the adjuster, so to drop it for a climb needs a good few turns.
2011 revelations are available with a dual air dual position damper, so that might be worth a look. (tftuned might know if the dual position damper will fit a 426)