To be frank, I don't think a dedicated killswitch exists for F-35s. Damn planes are so over-engineered and filled with future tech, 3 months of embargoes would ground %90 of the fleet.
But this debate about having true control over a 5th gen aircraft is an interesting conundrum. I think the solution would be to make "core" codes written jointly with but advanced coding seperate. Things that can compromise the aircraft are either; A) known to other parties in its entirety or B) completely secret to each consortium member. Cyber security suite can be seperate for example. Sure, this approach may require more work and resources, but it would end the killswitch debate.
If there is a sliver of possibility of partnering with Europeans on KAAN, this would be the best way to go at it. This doesn't eliminate the classic german moves like embargoing parts, but it would ameliorate the distrust a lot. And let's be honets to ourselves, we have every reason not to trust Europeans.
And I think aside from being kicked out of F35 program, the driving force behind the ”domestic and national” goal was get rid of that doubt constantly dangling above our heads at first place.I think the doubt alone is enough