If you really want to blow his mind, use drywall and cover it with Kerdi. See
www.schluter.com and watch their video. No plastic, no roofing felt, Kerdi is waterproof, and instead of it being behind the wall, it's right underneath the tile, so the whole thing dries out much quicker and is less prone to molding.
Sometimes it is just easier to scab a new stud along side of the existing ones rather than trying to shim them straight. Consider steel studs...nice and straight!, especially if you are going with Kerdi.