I'm not sure I like the battle idea for the pets. It might be way too easy for someone to do nothing but breed killer tendancies into their pet.

If you fight someone else's pet and yours dies, then what? Do you have to start all over? No one's going to like that.

On the other hand, I do think the pets should do a lot more than they do now. I downloaded the demo version a while back and was very disappointed (compared to plant and fish tycoons). The pet did almost nothing. Remember, people are used to The Sims these days and will expect a whole lot more from their simulators.