Ukraine

Gripen sounds like a perfect fit. From the little I know about it, I got the impression it can be operated, just fine, under non-ideal conditions. Like using roads as runways, easier maintenance with less personel than usual and so on. I learned that from watching very short videos, so you might want to double check.

I think it makes sense: Gripen was developed by a small country close to Russia, with no reason to fear anyone but Russia. So kind of designed for the defensive underdog role.

The F-16 and even more so the F-35, are more demanding on organisation and logistics, I believe. Great when you have the capability to double down on it, not so useful when your Hinterland is constantly bombarded. Like I heard they have trouble keeping electricity and water going. Not sure if maintaining a fleet of 35s is possible under these conditions. Fingers crossed they can make good use of the 16s.