Some airlines take military FE time, I can't remember which airline but I saw one that gave half credit up to 1000 flying hours (so they gave 500 hours of credit if you had 1000hrs as a military FE). I met a C130 reserve FE and I asked if he ever thought about trying to commission and go UPT, but he told me he was already a 737 pilot at UA and was content doing the FE thing. If I were you though, I would be going for the UPT slot, but don't count out the FE. I don't know of any airlines that take NAV hours.