Tested something similar to this about a month ago. Despite the fact that people say "the gear you should have while questing doesn't matter" depends on the gear you have going into it. My character copied a 690 shaman with enough quests to get him just above 101 ilvl from wod alone. I character copied my 742 shaman and went straight into the Legion questline. Yes, he hit 101 faster than I did, but I passed him around 105. I was able to pull more and kill everything faster than he was in the 50 ilvl less gear. We were the same spec with the same experience on it.
TL;DR - Despite what people say, gear does matter some. If you're going to cross your fingers that these methods aren't nerfed to dust before launch and go for it, make sure your gear is at least decent enough to not cause you to fall behind.