To be fair on zoos, there are some very good ones in the world that treat the animals very well. They have conservation and enrichment programs that make the animals as happy and safe as possible. And due to medical treatment they might live much longer and comfortable lives than their equivalent in the wild. Many species would be at a higher risk of becoming extinct if it wasn't for the work that they do at zoos. For example, animals living in the Serengeti may be at risk from poachers. The purpose of the Serengeti in the first place, the reason it became a National Park, was because the animals were being hunted for fun and people wanted to protect them. It's kind of like a giant zoo, if you think about it.
Obviously some are better than others, and nobody wants to see animals mistreated in the game. This is why I was outspoken that we shouldn't get animals in the circus pack when we heard it was coming to the TS3 store. I didn't want to see animals in small cages.
I wouldn't mind a zoo pack with a focus on conservation and enrichment. I loved Zoo Tycoon for example! But I think a Serengeti pack might feel more acceptable (as long as Sims only shoot them with cameras).