The Panavia Tornado was previously certified to carry US nuclear bombs

During the cold war. That's a very important bit.

The only approach that might work would be to forward deploy French nuclear forces on German territor

Are you sure you know how the current program works? Because that's how it does. The US aren't sharing nukes right now (that would violate NPT), the plan would be to hand off the weapons to its allies in the event of an invasion.