They can always edit the rate, situations, and conditions that they use skills.
For MVP versions, they could heighten the skill level of skills they use, too.
Pally could have Level 10 Pressure to sap 80% SP and deal auto 4K?

Perhaps a Level 10 Shield Chain? Players skills that require weight take the monster's attack power into account, instead.

Bio monsters..I think they should be paired with homunculi. Call 1 slave. Random Homunculi spawns and assists them. Demos, Terrors, occasional Mammo, cast time AD.
Champ...I see Snap, Critical Attack, and stand alone combo skills being used more often. FO when chasing or attacked with range like how Seyren Spear Boomerangs.
Clown/Gypsy...I see those two assisting quite a lot. Possibly even passive. AV like how Cecil Sharp Shoots, with a low % chance of Tarot. May even have things like area status effects.
Prof will be hell to deal with. Dispel, Web (especially when chasing), Wall of Fog instead of Pneuma, could possibly Energy Coat for more redux...
Stalker...Full Strip. Mixing up Tunnel Drive/Chase Walk should confuse players. Be extra fun if it can plagiarize.