Long ago someone already had the bright idea of making individual sims of tons of different animals all based around the same shitty engine, each with their own separate DLC and flood the android market with them. I was really interested in animal sims for a while.

I think we're headed into good territory though. Check out this clearly Harvest Moon inspired cat sim: http://cattailsgame.com/

Personally, I would like to see an animal-centric classic Gamemaker style RPG a la Chef Boyardee's Barkley, Shut Up and Jam: Gaiden with an audacious plot on the level of Cats & Dogs.