Is it possible to enlist as a flight medic in the Army Reserves or National Guard?

The hard thing is going to be finding an open slot. There are a few in every state, however we have literally had people retire as an E5 in that position because they didn't want to promote out of the slot. Your best bet is to talk to NG and Reserve recruiters in your area to find out which units have flight medics, then contact that unit with your qualifications to see if that are anticipating a slot opening soon.

Flight Medic slots are hard to come by, as you have to be a Medic for at least a year before you can become a flight medic. Considering your already established skill set, you may be able to get that waived (unsure but one never knows). Talk with a Recruiter and also talk with the nearest medical aviation unit nearest you for slotting requirements.

If you honorably discharged w/ RE1 you’ll be gravy. Too easy. (This is an assumption in regard to your situation, any other kind of discharge or RE code may take a waiver)