I think a good idea would be that since we have similar things for raising up chickens, rabbits, and doves, why not add in a squirrel pen and/or a rat den so we can nurture high quality tasty squirrels what with their cute tails and/or rats with their necessary protein and exciting plague taste? It can use a similar food & water system to chicken coops and rabbit hutches, and unless Jorb wanted to add special graphics for male and female squirrels/rats, all that'd need to be added is baby squirrels &rats and pretty blood splats they make when you squish one.
...Besides, I'm all ready and hoping to raise squirrels. I got a cupboard full of squirrels in my basement lying in wait!!