Basically joyful but with dismemberment.

Buddy's a frail gal with a sharp sword and Rando's a big boy but beat to shit; It would make sense that they would try to have a battle strategy other than "I stab the guy in the throat 28 times and you spam Machine Gun Fist + Fireball".

Of course they would have altered movesets, with buddy focusing more on survival (+Hide and +Poison on an open wound) and Rando having some kind of stun with Dropkick, maybe a guaranteed stun on Rando Stab (uses all SP and hurts him) or +Fallen on Buster Punches and Rando Bomb (Same deal with Stab).

You could cut off or at least damage Fardy's arms so he can only unload on you with one gun; Dropkick Big L's head when he's gathering strength so maybe he doesn't send you to Hell. Dice and the other Joy Mutants could maybe regenerate limbs / heal them every turn.

also it would be real fun to chop off everyone's PP