Great project and great learning experience. Don't know who put you up to it, but I like it.
You have some pretty good ideas so far. I have attached something similar that has circulated on the Internet, but needs a few modifications to be better.
Note.....you only need one nest box for each four birds, so a big mistake folks make when designing these is wasting precious space with extra nest boxes that won't get used. You will also only need one roost perch. In the diagram, use only the middle one and keep it a foot from the back wall, halfway up. About the height of that middle chicken is where you want it.
Rather than putting the pop door in the middle you could put the pop door off to the side in one corner, and a single next box to the side of it. Where the nest boxes are shown, it would be better to put either an opening window with screen, or if you live in area where it does not get much below freezing temps, just leave the opening open and cover it with hardware cloth. Use the same opening.
The ladders I see on these always look cute, but you don't need them. Better to have a small flat perch in front of the windows for the birds to hop up on to enter. For some reason, birds are expected to fly up to roosts and next boxes, but must have a ladder to climb up to the pop window?
Slope the roof as shown, but do not use a metal roof. Moisture will condense on the metal and drip down on the birds. I'd suggest plywood roof, with roof shingles. If this is really temp, just paint your plywood roof. Same with the floor. If this is a short term project that you don't intend to keep you could just use bare wood. Better is to paint the floor.....exterior latex paint.....high gloss. If you want to keep it around and use it.......you probably will.......put some vinyl floor down and paint the walls and ceiling bright white. This will make it easier to keep clean and make it bright inside. Make sure your pop door is high enough the litter you put down on this floor will not flow out when you open the door, or clog the opening so it won't close.
Raising the coop as shown leaves a place for food and water and a bit of shade, which the birds will need.
Perhaps I've given you too many ideas (cheating?), but you still have to finish the design and actually build it. Great learning experience.