Lets just all hope that if Southwest does bid for Frontier, that they actually merge the two lists, rather than run two separate airlines. If this happens, I would say it is a good deal for all involved.
If they keep Southwest and Frontier, it will be bad for all involved. They will wipsaw one against the other (Look how much lower Frontier pilots are paid than Southwest pilots), probably slowing sucking routes/gates away from Frontier, and it would just be a disaster.