They give stats based on your skill level (i assume just combat boosts, but skilling boosts is a possibility), every mob kill now drops bones (can do multiple types of bones based on difficulty of monster, can also add local market perk like woodcutting & fishing for double bones at tier 5).
This can be used as a normal skill trip to level up your pet skill level (like cooking except you only get experience).
Adds a new pet token which allows you to unlock new Pets for purely cosmetic purposes (can either be buyable in local market, or $, or do like the other tokens where they are buyable in the player market, not sure how you would want this done). So for example base pet is a dog, but you can unlock a dragon for 1 pet token, I think that would be super cool.
Not sure if it should work in raids, or maybe even add a hardmode with pets.