Unless it's going by the "so hideous to look at that it turns people to stone" rule. I suppose I might just need the eyes, would be easier to carry, and there's mythological precedent for not having to worry about preserving it. 

I wonder, if we turned the eyes into a key-chain would the resulting keyblade have a chance to proc stone when it hit?

*Edit*

Thinking more, if we did it that way we could get Cheese to craft more magic accessories to increase the proc chance and pile those on the one who gets the hypothetical medusa keyblade.