Need some more variety in magic pets, especially since they can be such a potent counter against massive damage attackers but most seem to have similar attack patterns. It's extra hilarious that they're weak to dragon who are typically putting out big number hits anyway and likely to hit the magic family 40% health damage cap regardless.
I would very much like to see a few more ideas imported from *cough*pokemon*cough*. Stat-switched attacks, such as damage based on speed, and reversal stat attacks such as damage based on speed lower speed=higher damage (the 'extra damage if goes last' attacks come close). Some more variants of the 'if enemy has greater health' such as 'if enemy has higher attack power'.
I definitely don't want them to go full on 'evolving' pets, but a few pets that are received by leveling their predecessor, or 'breeding' two level 25s of different species, or some other new mechanics for how to get some pets.
More pets with Feign Death and setup attacks. As things stand the only pets with Feign Death aren't bringing much to the table in terms of set up and switchout. Whereas some other setup starters such as a rare candied Ghostly Skull can do great work, then sacrifice on their immortal undead turn for their big debuff/setup. Likewise exploders unless countered with multi-hit kills (Or a stun, or Wind-Up for most) do a great job of setup and destroy.
I think the number of forced switch attacks is good, between Enchanted Broom's Sweep and the number of Death Grip users. Possibly propagating a clone of Death Grip or Sweep to one or two other families.
A little more attack variety in some of the 'common' recolor pets. A new Water Strider with one different attack, new frog with a little something different, definitely one or more of the plant/treant/ancient/lasher elementals with some variety. Rats certainly could use a superstar who brings something different to the table. The Lava Crab and Fire Beetle were good examples of recolors with a bit of variety to them. The Wanderer's Festival Hatchling is at least different as a turtle, although personally the one attack it gave up for variety was my favorite of the type. Mr. Bigglesworth obviously is excellent and interesting on that score. Moths, rats, and roaches are some of the worst offenders in my opinion. Too many types, no variety. And their isn't enough variation in their standard attack set to really make them interesting or dynamic as it is.
A baby murloc, dammit.
Furbolg Shaman, humanoid with humanoid, magic, beast and elemental attack choices.
omg I want a mini Abomination soooo bad. I've wanted a tiny abom pet since before there were pet battles. Undead with some humanoid and undead attacks, seems an easy win for Blizzard to make.
A Wretched, give it a Silence themed clone of Kick/Backflip, a Fel oriented attack or two, and an 'idle' animation of some sort of arcane drain and very short lived transformation into a belf around magic family pets.
A mini-Shredder mechanical pet to go with/against our Tonks.
Aarokoa, clone of the harpy youngling.
Frenzytooth, aquatic Rip, Swarm/Flock clone, Blood In The Water
Heroes Of The Alliance/Horde mini-pet versions. In game explanation that they're magical toys/figurines of the heroes. No pet family so no strength/weaknesses, and some signature attacks. No alternate attacks, they have their 3 'signature' moves. Mini-Jaina with Ring of Frost, a Water Elemental clone of Sentry Gun, and something arcane-ish. Garrosh with a Mana Bomb ultimate and 2 other attack slots consisting of gloating like a Mogu. Saurfang and cleave! Thrall, a heal, a shield, and an elemental attack.
A Kodo Runt
one of the double-headed vultures with a double-Peck attack in place of one of the usual avian tier 3s
Mini-pet variants of each of the Spirit Beasts.
A Worgen mini-pet, complete with 'Two Forms' that flips their Attack/Speed values. Frankly a complete set of 'racial' humanoid minipets each with a signature attack or two.
Honestly, I could probably keep going. =)