Interesting thread. Read only half of it, and agree to most. I'd love to see a good spread of animals, but if each specie comes in a few versions, say cows can be brown, black, white or spotted, I'd survive with just a handful species. And I wouldn't need to be able to interact a lot with them either, I recall a cc "circle of life" chicken farm object for TS2 that was rather static, but I had lots of fun with it running a chicken farm.
Most important to me is a good system where I'd succeed or fail as a farmer. Like a business. Animals reproduce allowing me to sell off a few or even stuff my fridge with meat, eggs, bacon, and milk/cheese. Sims could even sell off wool and fur, or craft related products at home. We might need a new freezer object though, intended for a barn building storage room or a basement. Animals health should be important, like there being a threat in form of deceases or even wild animal attacking say sheep, needing the farmer to repair fences that fall down during a winter storm (seasons). I think a farm EP could focus on animals and the barn equipment, we could do fine with the crops we already got, corn/hay to be added perhaps.
Really would get this EP!