I support the change, have concerns with the implementation. How about this:
Change all AAs to None if that is necessary to implement the TE system.
Put all nations in Peace Mode, but suspend the happiness penalty for a period of time, say 7 days or whatever seems reasonable. After that time the penalty is reinstated at whatever level they would normally be. That way actives could rejoin their alliance then switch back to war mode without penalty. Semi-actives that miss the deadline will take a hit but at least they'll be protected. Nations at war before the switch would be forced out of peace mode at the deadline.
And everybody will be Happy, Happy, Happy.