I think it would be on the small side for three... but you could try it?
What do you bed with? I think it might work if the whole bottom was clear for running. You could do that if you made a platform on one side, just like on the top floor, and let the ramp start from that (it would also make it less steep). Then you could have some kind of disposable bedding in the bottom and lose hay. I think pigloos and the like would take up too much floor space.