One of the suggestions someone made to me when I was building my coop was to design the roost over a board that could be slid out and easily cleaned. Most of the poop inside the coop is on this board, and mine slides out through the next box roof/door. With 25 chickens, you are going to have a lot of poop. Since you are going to replace the sheet metal with plywood, you could put a row of nest boxes down one side, with a roost and poop board (or boards) just over the nest boxes.
I don't see much ventilation. Make sure you have adequate ventilation. With your 8 x 12 A-frame, and 25 birds, you might want to open the top foot or so of the roof, building a secondary roof to cover that, so that fumes and heat can escape. For the summer, I'd put some vents down low as well, so that cooler air can come in while the hotter air escapes.