I had plenty of mil hours and still paid out of pocket for my ATP. I think having all your credentials in hand is pretty much expected if you want any major to take you seriously. I don't think Spirit has a program for repaying for training, they want you to show up qualified in every way except for the type.

Lots of regionals would probably be happy to train you up in return for a year or two payback contract, and with some regionals, in that 1-2 years you'd get paid better than a first yr spirit FO (after bonuses) and possibly get enough hours to be interesting to a Legacy. I have a friend in a similar situation (ex-military but not a mil pilot). He is starting off with skywest, and will have a good chance at ending up at a legacy in a couple years.