Combat system is near perfect, but could use a 'training mode'

I used to think the character swap mechanic was jank, in that your partners' AI couldn't build ATB as well, and that character swapping being optimal looked weird.

But after 100%-ing (thanks to guides) the game, I've realized it's extremely near perfect, with this exception:

There's no true "Training Mode", where you can load any playable character and learn their mechanics against an enemy with infinite HP, and attacks you.

I love that the hardest challenges have you solve a puzzle, and that there are several solutions to each puzzle, but for example, the Cloud and Zack challenges, most people are going to go for Cloud-specific strats, because there's just not enough learning ramp for Zack, unless you go out of your way to learn him.

A training mode where Chadley just lets you play as ANY character combination, including Zack and Sephiroth, in the challenges, would be awesome as well. We want to learn these characters outside of their limited and crappy Chadley tutorial missions!