An interesting concept, except for the fact that you would have to play through the game and gear your party up to max 12 times to face them all. Thats like 1200 hours of work.

I never felt that bosses were a very strong part of FFT. They kind of went against the whole design concept of the battles, to have one single very strong opponent. That being said, weapon encounters wouldn't necessarily have to be single enemy encounters.

I'm always game for the concept of more stuff to include in the game though.