In fact, the method of extracting sims and pets this way was built into SimPE, with this kind of template-sharing in mind.
As for pets - I don't know. What I would do is register the breed via telephone in game, then go to CAS and package the pet from there.
Leefish, I'm not quite following. Certainly you can make pets in cas, but I'm not sure what you mean by "If the pet is in the hood is it not available in CAS to package?" No it's not available in cas, just like sims in game are not available in cas unless they have been downloaded or extracted. This is Esme's hood I am extracting for her and there are a few cats and one dog as well as human type sims. I've Googled around but can't find anything on the sharing of pets.