Is that already a taken title? Ah man. Well yes that's the idea. Key thing is probably going to be that the creature transformations CAN'T happen all the time, otherwise it's like what's the point? That's basically just an OP character with every ability, so I think we'd have to limit that somehow... possibly only allowing it to happen by contacting a mage who has limited mana, or transform pads/objects. It could be that the main player moves with WASD controls and the mage moves with arrow keys.
EDIT: You know what? I'm buying that.
Yeah I was kind of thinking that general idea where the player has to be in designated areas to do it, but we could also try mana potions to resupply that stuff. I haven't fully thought out the mana potions, but fetching them for the mage just sounds fun. Also maybe the mage can shoot transformation spells at the player, we'd have to be careful with this idea here though because that's technically making the gameplay easier unless we design some difficult levels around that idea.
MAYBE we don't even need a mage. Maybe we just collect mana potions and that's how we can transform. The player would just have to use/count them wisely, or reset level.