If you enclose the ENTIRE bottom with 1/4" hardwarecloth, including the floor (ground), all tight with no gaps, that will pretty much keep rats and most mice out. Make the front hinged so you can open it. Then get, or build, a plastic or plywood tray that exactly fits that area. Put a dusting of shavings into that poop tray (to absorb odor and to make it easier to clean), then just pull it out and clean however often is necessary. I.e before mold develops LOL
Good luck, have fun,
Pat
Good luck, have fun,
Pat