Well, the We seems to be a remnant of a Pre-Skaven underground ecosystem, so we should look into other pockets of surviving wildlife and see what can live underground and feed the We, I am hoping there are
nugs somewhere, so they could learn to farm their own food.
As for a short term solution, I kinda like all options? The gauntlet seems like the simplest option, but I don't want the Drahz forces to be there forever, we have to deal with the source eventually so they would have to change again.
So the Badlands seem like the more permanent solution, unless we go for the trade (which would be expensive I imagine, unless we really get into the goat business with the goo). The mountains could work as well, but I feel like they might accidentally run into some giant eagles get in trouble for it.