Be sure you've read all the messages about WU in this Part 135 forum. I don't know how long and if Delta will keep propping them up if they don't become profitable.
I don't remember if they have a training contract, but be aware about that if there is one. If they file for bankruptcy and cut pay could you still be on the hook for the training contract?
I suspect they have a lot of pilots heading for the exit door so you could do well seniority wise if the company remains a going concern. Just be sure of what you're getting into. I haven't seen any current WU pilots post on here in quite some time, hopefully one will show up and can give the latest info.