This one is a great idea in my opinion: why not create a situation that if more than one player casts the exact same spell, there would be a chance for 2-4 players to cast a combination spell. For example, if 2 people were able to successfully summon a firecat against the same enemy, a pack of firecats would appear instead and attack the enemy instead. This obviously should be limited to a few spells to avoid overpowering a specific school or level. I would probably suggest at least one area spell and two single enemy spells for each applicable school. Sun, Star, and Moon shouldn't be considered a part of this idea. Here's how the battle would work in that regard, implementing some restriction ideas:
Wizard 1: Fire Cat
Wizard 2: Sprite
Wizard 3: Fire Cat
Wizard 4: Fire Blade
Order of battle:
1) Wizard 1 casts Fire Cat successfully 2) Turn skips to Wizard 3 to see if his spell casts successfully with a restriction of a 10% decrease in accuracy. 3a) If Wizard 3 successfully casts, both Wizard 1 and Wizard 3 spells will become Pack of Firecats and attack the targeted enemy. 3b) If Wizard 3 spell fizzles, only Wizard 1's firecat will attack. 4) Under either circumstance, the turn counter will rotate back to Wizard 2 and he'll cast his spell. Then, Wizard 4 will cast his spell. 5) If a team spell works, the wizards should be affected by some kind of side effect like a stun for a turn or backlash from the spell.
