I'd be real careful about hoping for a merger with WN. They aren't ALPA, they're SWAPA. Spirit was ALPA. Big difference when it came to a merger. WN doesn't subscribe to the ALPA SLI policy of "Career expectations, longevity, and status and category".
Sure, they can't staple. But, there's no guarantee of any sort of fair integration. You might lose a lot of seniority.
And those guys at WN are probably some serious pipe hitters over there, with experience I'd add (AirTran).
Guarantee, they'd run circles around F9.