I've never done role play, but it might be kind of fun. But I always thought it would be a bit distracting from the sex (read: "orgasms, etc").
But, as a ballet fan, it might be fun to be a Drosselmeyer to someone's Clara. I love the frilly gown and the bow that Clara wears in the Nutcracker (which I just saw). I might replace ballet slippers with something more sleepable (but keep the tights), like maybe these pink satin booties that I saw on an ABDL clothing site one time. They have lace and ribboning and such, IIRC.
No clue which act I'd try to act out, or whether I'd want to roleplay some other way, with the Clara costume being the star.
So, playing Clara would be playing a 12 year old girl; at least as I've read. But I'm not sure exactly how old Drosselmeyer is (I'm 44, and my Clara would need to be 18-22).
ETA: Oh, and to relate this to medfet, since this is mainly a medfet board, she could be having asthma trouble or immune system trouble, and need to be wearing a mask. What kind of a medical exam could be done within the context of the Nutcracker is beyond me, though.