Downside
Shades of the Iran F-14 deal, sell/give them one of your best, government changes and then wish you had them back.
Indeed blowback is a concern. I would think that with the F-35 being so software dependent, and tied to the ALIS system, that operations by a country that has gone "the other way" would be much more difficult. Perhaps even a few lines of code that the jet could be "bricked", or not receive an update it needs. I know some countries were concerned about not having the rights/or the full code.
It is one thing to keep a Huey/Cobra, C-130, F-4, F-5, F-14 etc. running with little outside support- and the Iranians have done an impressive job- but the amount of software on those airframes pales compared to the F-35. It sound like buyers will be very tied to the LM software codes (some perhaps more than others).