I feel like Sims 2 had the best pets, complete with pet shops. I love every single one of your suggestions though, I especially think pet clothes could be cute since I typically put my dog in a sweater during the winter months. I would also love a vet career, I had to get that as a mod in TS3, so I would love to see it just made into the game. I loved the small animal aspect in TS3, but as far as I know (or maybe I've just forgotten) you couldn't just buy them, you had to find them in the wild and it wasn't guaranteed you would successfully catch them.