I MC'd a small session where Meat the Faceless had Pickle (Norman) and relied on him heavily for almost everything. He flavored that Pickle dulled his senses whenever he usedRasputin and played Bonefeel as him blacking out and Pickle getting him where he needed to be. I hinted the first time botched a weird roll that if he opens his mind too wide he might fall out of his body... and Pickle might not be nice enough to let him back in.
The player loved the idea. Though I think all depends on how they take your spin, you know?