I totally love the idea of this, and it's a pretty great implementation, too. Good on you, Edro.

I'm a little concerned about the Familiar Class ability, especially in combination with the Extra Familiar ability. A wizard with what amounts to two super-powered cohorts is a touch more scary than I hope you were intending. Even sticking to core, you've left barbarian and (Full BAB) rogue as options for the familiar, both of which can be decent options on their own; layer those classes onto a powerful monster and you might have a mess on your hands.