Mucking around with a few concepts in herolab and I just stumbled across this archetype for your familiar . . .
An egoist believes itself to be the real master in the relationship - the power behind the throne. It often attempts to communicate "orders" for its master as best it can, interfering in matters ranging from spell choices and tactical combat decisions to its masters love life.
So appropriate for my usual choice of a cat familar.
Incidentally what I was looking at was the figment familiar for an arcanist/summoner mix.
Back in 3.5, one of my players rolled up a character who was, on paper, a gnome sorcerer with a toad familiar. But in reality, the gnome was the manager/agent of a powerful wizard who had been turned into a toad.
Every spell worked through the familiar; acid splash and burning hands and grease were breath weapons. Instead of summoning monsters, the toad itself transmorgrified into various things--bloating up into a balloon to scout ahead (or behind, depending on the wind), collapsing into a boneless puddle to ooze under doors, or puffing up into a gigantic, horned monstrosity that swallowed enemies whole.
The toad also functioned as a handy haversack.