"Priority waitlist" is a mess, since they won't protect you. BUT Southwest's system can be gamed in this scenario if you plan in advance. (I've got a million SW tricks)

Not that I would ever do this , but "what I've heard" you can do is buy multiple one-way tickets during an expected busy day on Southwest. Since they will all be at capacity or oversold, you can do this for flights A, B and C:

Flight A: ask to get bumped. If yes, take voucher and ask for refund of ticket (they will gladly do this to relieve themselves of the obligation to get you there). If no, get on plane, call the 800 number and cancel the other two flights (no $75 penalty on Southwest!).

Flight B: if bumped on A, repeat process.

Flight C: if bumped on A and B, get on this flight with $XXX dollars in vouchers for being a couple hours late. Have a drink. Enjoy the holidays. Repeat for the return trip.