Considering I'm figuring he'd end up as a Normal/Ghost Enlightened, he's not going to have too terribly many ghostly traits that'll trigger your Rose. But, he does have a wild personality that might make him rather rough company to be around.

Regarding Mami-- I love that idea. He hangs around a tough lady in canon who helped him get oriented into his new state of affairs, and he'd definitely be interested in how the Valkyries are like.

He's also fairly physical, so arguments that turn into impromptu sparring might be hilarious.