So let me get this straight--your company (USAirways, United, or AA) will let you take an LOA long enough to get their minimum hours at TSA, then hire you back as an FO?
I've heard of FAs getting special consideration, but that sounds like a long-shot. I guess it's worth trying.
Just make sure you don't fail out of training at TSA.
If you're looking at getting hired at 250 hrs, I'm pretty sure they aren't doing that anymore. Neither is PSA. It might be this time of year, or the fact that they loaded up on apps when they were listing that as mins.