I'd agree that, at the 'lo' end of the spectrum, a modernised OV - 10 seems a pretty good choice. Indeed, I seem to recall that a couple have recently been flying operationally to prove the validity & concept.
At the 'hi' end, I'm pretty sure the A - 10 fits the criteria perfectly (save for sfc, I suppose) - assuming the 2.5 hr mission duration includes transit as well as loiter. If not, a 600 gallon external tank has been trialled which would certainly take you well over 2.5 hrs.
I really don't know why you'd need to look further than the above. Certainly, in the case of the A - 10 - it's cheap, carries pretty much anything you might want to carry, it's built like an outhouse and frankly, if one appears over the battle space, it's a very brave soul indeed who doesn't soil himself and run like a girl... It's so tough, that not even the air force or congress can kill it!
Last edited by JG54; 17th Jun 2017 at 16:42.
Reason: Addendum