if I'm not mistaken, you're in residence in the other body. As in, you, as the possessing spirit, are casting it on the body you are inhabiting.
If I'm mistaken, and you're casting it on a body with the soul vacated. . .then it's neither an animal nor a being. . . .it's a meat puppet. All "m" spells would fail, it has no mind at all, you can't charm, command or familiar it.. . . The logic is akin to:
"If I kill a cow, cut a steak off and cast lifekeeping or preservation on the steak to keep it alive, can I make the steak a familiar?"
Beyond that, the 10% caster's weight limit would pose problems.