I don't know if vacuum down a tire would damage it, I see your argument, but I'm not aware of kevlar belts being any more delicate or brittle than steel belts. Distorting tires to much I could see causing damage, at the same time if you've ever mounted tires, especially bigger lower profile tires, which many vehicle have today, the tires are forced, stretched and distorted terribly during mounting and are not damaged.
Sidewalls are designed to bend and flex, cause they do bend and flex constantly as the tire rolls. This why you can't patch the sidewall of a tire and the tire is ruined with any sidewall puncture, it bends and flexes so much the patch will be pulled away from the bend and flex. Its not because sidewalls are so delicate, it because sidewalls can't be repaired. I suppose there is only so much distortion they can take.
I would imagine purging would work well also, you'd just need a thin tube to fit in valve stem with the valve removed that had some space to spare around it, pump in the nitrogen and it forces out the air. Sure it mixes as you pump it in, that is why you pump in more than the actual volume of the tire. Purging has been show to get almost all the old gas out and the tire wouldn't be distorted while you did it.