Hi, still considering a built in coop or one of those coop tractor thingy's. I only want at the most six hens for pets/layers. Can they live in one of those portable tractor houses and have a HUGE pen to freely roam in at will? Or do they need the coop with the places to roost and all that other chicken stuff they do. What about keeping warm in winter, being portable and with the bottom hole to access the house how does one keep them warm and cozy?