I think the lack of animals during development was due mostly to limited time and processing reasources. They would have had to hire another modeler just to do the animals and the extra burden on the computers (remember they used less powerful comps then). I am finding the game chugs and kicks out often just because I have so many addons (approx 650mb!) for my full version. My clean version which is on a different drive partition and has no addons but the BIS ones runs super smooth.
I think it would add alot to the game. Farms would look more like farms, guard dogs and birds flying overhead would make the game more alive. As for the ftards who would just use the editor to blow up cows, well I think they would be in the minority.
We do have one animal so far the seagull, maybe BIS could add the seagull under the civilian-man section, or under aircraft to it can be added to give some life to the game.