To repeat what others have said: Look at a pre nup to be done on seniority before any deal is made. SWA has never integrated anyone else into their club. Do not expect altruistic intentions from the SWAPA negotiators. There has been impending stagnation in the right seat at SWA, and those F/Os won't be happy to see the F9 guys come in ahead of them, even if it is deserved. Any prenup will trump the legislated seniority protections.
Frontier is bringing jets and routes to the table. Though the Airbus may be replaced by the 737 it's not like those jets have no meaning. Those are viable routes they are flying and if F9 had the creditworthiness of SWA there would have been no CH 11. Remember, it was the credit card holdbacks that did them in, along with the high fuel prices. It wasn't the business model that was the problem. Given a better economy Frontier could have built up to Air Tran's level of growth. Frontier pilots should be a part of any deal.
SWA is a very smart airline. They will do what is best for their company. Unfortunately, there is nothing in that charter that will make allowances for how great Frontier's people are and should be taken care of. That is not the way of big business (although it should be).
Good luck to the F9 ers.