Paizo has the same thing with the
Nature and
Mammoth spirit
Shaman, whose familiar turns into an animal companion at level 16 while retaining all familiar abilities. It also has something similar in the form of the
Courtly Hunter, which gives animal companions a familiar's int progression. One thing that comes to mind about this kind of companion is that it will get very high AC because it obtains both the natural armor increases of familiars and the ones of animal companions (assuming the natural armor increase is treated as a special ability and not a statistic).
Mauler familiar archetype gets a bunch of bonus strength, but can never speak (and lets you use
Mauler's Endurance to give it +2 health/lvl). A
Valet familiar gets all teamwork feats and item creation feats that the master has. The
Figment familiar archetype makes your animal companion auto-rez whenever it dies and gives it up to 3
evolution points like an Eidolon, reassigned each day (Improved Natural Armor, Skilled, Pounce, and Flight are all good picks, among others). You can also use the
Prankster archetype to give your animal companion a bunch of at-will SLAs and dirty trick maneuver feats. You can also use the
Evolved Familiar feat, which is a slightly better version of the
Evolved Companion feat because it lets you give your companion Pounce and Reach evolutions, assuming that this animal companion form still counts as a familiar for the purposes of feats anyway.
Other than that you're mostly doing regular animal companion stunts. An optimized animal companion is already a familiar on steroids anyway, so this is mostly a buffed animal companion with a bunch of good perks on top. Starting with int higher than 2 also means that the animal companion can take any feat starting at level 1, so there's that. Normally you'd need to play a
Human with the Eye for Talent alternate racial trait for that, unless you're a Paladin or getting a magical beast as your animal companion anyway.
If you want to make your animal companion crazy, you're generally looking at WBLmancer builds (possibly involving UMD), polymorphs, buffs like
Divine Favor and
Blade Tutor's Spirit with Share Spells, giving it SLAs with spells (ie.
Imbue with Spell Ability,
Blood Song,
Spellcasting Contract), giving it a
Ring of Spell Storing (use
Hand of Glory necklace or
Extra Item Slot feat if it has no ring slot) and unusual feats like Obediences,
Eldritch Heritage for a Sorcerer bloodline (
Exotic Heritage for wildblooded variant),
Item Mastery feats, or
Planar Infusion (using
Improved Planar Infusion and
Greater Planar Infusion in particular) to give your animal companion special powers. Other stunts are just giving it
Master Craftsman and
Craft Wondrous Item or
Craft Arms and Armor and making it craft magic items for the party (You can even give it
Master Alchemist and make it craft alchemical items during downtime).
Otherwise it's mostly vanilla bruisers where you try to make the numbers bigger and equip your animal companion in a nice suit of animal barding armor to give it better AC along with whatever magic items you feel like boosting it with.
