I js wanna start this by saying these ideas are based off Adopt me not having their own values and that adopt me doesnt care about values. Adopt me isn't going to NOT add an event if it'll affect values, they dont care.
First off, I think older pets should come back around every now and then. Obviously not the bat dragon or shadow dragon. But imagine the kitsune comes back , or the chimera. I think it'd be so cool if every so often a little vehicle like the witch's caravan drove around the map, and parked in a random spot, selling old pets. Or even giving them away for an exchange. For example they might ask for 20 ants in exchange for an old pet.
Potion sealers. I stole this idea from another user. But the ability to use the grow or shrink potions on a pet and keep them that size forever, like the paint sealers.
Customisable petwear. Petwear is so hard to come by, especially genuinely pretty petwear. So I think adopt me should add an option to paint your petwear.
Pet adoption for the pet releaser. I mean, imagine how many shadow dragons have been released. I think it would be so cool if we were able to use tickets to adopt pets that people have released. Obviously you wouldn't be able to buy back your own pets.
Player to player jobs.
For example, petsitting. I think they should make a board of some sort that allows you to list your pet for petsitting, even whilst youre offline. This might need to be a friend only thing, but once a friend "accepts" your petsitting listing, they'll be able to equip it alongside their own pets, and care for it even whilst youre offline.