I maintain that Chain of Memories would have been a good game had they made two simple changes, then some easy followups:
- Keep the fights 2D for the love of god this kind of fight system doesn't work in 3D
- Cards are special moves only, and smashing a motherfucker with your keyblade is a free action
Think Mega Man Battle Network, but with free movement and a focus on melee combat instead of distance combat. Keyblade cards are for either powerful hits or what the game currently has as sleights.
More specific changes I'd like to see would be
- Specific keyblades can be equipped for differences in attack style. Think KH2, which had come out already by CoM, where keyblade differences are minor stat differences, and abilities that come attached. Elemental damage, increased drop types, combo plus/minus, lucky strike, etc.
- Make Riku's combat function exactly like Sora's, but with different cards and keyblades. This would accomplish feeling different enough to not feel like the same game twice, but wouldn't suck completely. Perhaps a greater focus on risk/reward playstyle.
The Birth By Sleep/Dream Drop Distance combat systems are what I think CoM was going for. A selection of special moves you can pull off that feels different enough from the traditional hack and slash, but doesn't completely drop the hack and slash source material and then haphazardly paste it back onto the gameplay at the end.