True about the F-5 but man is it a beautiful jet. It's been one of my favorites forever and the Tunisian ones are so well maintained and also look like they went through an upgrade in some avionics and possibly an MLU as well.
Gripen is an excellent choice. South Africa enjoys their fleet of 26 Gripens although I believe they've lost a few and are down to 17 or 18 of them if I'm not mistaken. They're outstanding and the SAAF fly those things around like it's no-one's busy and handle the parts & maintenance without any issues at all.
Also, the Swedes, according to
@A.P. Richelieu are a bunch of snotty, noses up in the air snobs who won't sell the aircraft to any non-democratic country (no offense, Rich.) Their standards are finicky like that but in this case, with a wonderfully fledgling democracy like Tunisia, I bet you SAAB would jump at this opportunity in a heart beat. And with Tunisia's good relations with the US, parts for the Gripen engine and weapons and other things shouldn't be an issue at all. I actually like that choice.
Start out with 12 Gripen JAS 39Cs possibly @$40 million per and keep the 12 F-5s (they haven't lost any of those, right?) and have that compliment of 24 fighters working together I think is an excellent way to start.