Other folks can advise you better on that than I can. I just rake it out from under the coop into the yard every few months. Composting is probably a much better idea than what I do.
I like your coop, a lot! Some things I would change like the roosts as others have previously mentioned. One thing you will find though is that chicken poop will not fall through 1/2 x 1/2 HWC. I originally had that under my roost, but changed it to 1 x 2 welded wire. It still all doesn't...