I haven't tech packed any insulated pants, so this is totally off the top of my head & could be a misfire! If they're an insulated pair with inner lining & outer shell, they might've been constructed by sewing the ankle openings together inside out & then flipping, which usually means you have to take the waistband off to open them up & get to the original ankle seam. If 3"-4" would require moving the powder gaiter, that's usually attached to the lining & would almost definitely require a rip-n-flip. In general, there's a hell of a lot of weird detail work around the ankle of most ski pants, which isn't necessarily straightforward to shift up, depending on how the original pattern was cut. I would think a lot of tailors could cobble together something & more-or-less seam seal it, if the gaiter doesn't need to move, but I don't know that I would risk letting a random local tailor experiment on a good pair of ski pants if they haven't taken any apart before. You'd probably be better off shipping them out to someone who specializes.