Bear: Already one of the most used tames, doesn't need any help.
Chicken: Simple recipe (steak and eggs) for new players.
Cow: Maybe some type of herd buff, so raising cattle would have a point.
Bull: This is a big one, Bull should gather thatch well. Why in the world is Thatch a choke point in this game lol.
Crow: Maybe a buff that finds dead bodies in the nearby area, since crows irl are kinda sketchy creatures. But with the intelligence buff they already have, not totally needed.
Razortooth: No change needed, they are pretty good as is.
Shieldhorn: Should be the epic Thatch gatherer!
Elephant: Already pretty good as is.
Giant Pig: New phiomia is fine.
Giraffe: A pve buff would be nice, otherwise there isnt really a need to see other peoples territory markers farther out. Even on PVP who really uses that feature...
Horse: Already pretty good, but would be nice to see something like the lasso from Ark to make it more fun.
Lion: Seriously, the grab attack doesn't work on PVE.
Monkey: Again, doesn't throw poop on PVE, maybe some sort of passive buff would be nice. (Side note, people rarely use shoulder mounts because they die so easy)
Ostrich: Pretty good mount as is.
Parrot: Fine as is.
Penguin: Fine as is, I don't expect much from a penguin.
Rabbit: SOMETHING, this needs a buff, or reason to have this evil looking creature on your shoulder. Maybe it would be easy to breed them, for noob food or something.
Rhino: Should get some metal from normal nodes, just like you do with a pickaxe.
Seagull: Should have a sea buff, so you really want one on your shoulder out at sea. Otherwise no one tames these.
Sheep: Pretty good as is, more stam though.
Tiger: Slight faster would be nice, but otherwise good.
Vulture: An ability that goes along with corpses, or maybe you get a buff when you feed it spoiled meat. Something.
Wolf: Not too bad, but should really have the pack buffs/abilities from Ark. That was awesome.