Ive been told you can control each character instead of using the gambit system.
You can, but according to Shouta and Red Scarlet, the game will take _forever_ to play.
Make no mistake about it, the Gambit system really does save you a lot of work. On GAF, Bepbo said he made a pizza during a really long boss fight. He put his controller down, went into the kitchen, and made a pizza. Everything was automated and he didn't die.

I used to have one of Scarlet's videos where she's fighting a tough boss -- 10 seconds into the video she puts the controller down. And the AI does the rest for like 7 minutes until the boss is dead.