Familiar is Fm, the "m" being important here. . .essentially you'd be casting the spell on your soul, not the body. It's a mental effect spell, and the only mental to cast on in that body is you.
I think that is valid logic, in the sense of attunement of your aura to an object (That's actually what the attunement skill is doing.)
I'd certainly consider a caster who knows "familiar" to be one up in researching a new spell "Body attunement". . .
The sort of thing you'd find on the "Bodysnatcher's Ways" list. It just doesn't seem to fit the logic of familiar, which is bonding an animal intelect to your aura. . .what you're talking is more akin to a skill, or a spell that aids the manipulation of matter.
