how would you guys feel about a magic system where humans can only gain magical powers by consuming monster body parts? like to be able to shapeshift the character would need to eat a pound of werewolf or changeling flesh? or to cast fire magic they'd have to eat a fire elemental's core?

Mechanically this works off of synthetic dream machine. You pay hp for spells and each level up gains you 4hp. Spells would have a fixed minimum cost thus enforcing certain level requirements. You would gain access to certain groups of spells if you eat a corresponding monster core, like you have access to all fire spells if you eat a fire elemental core but they still have hp costs so you can't just cast fireball at level one.