I've noticed folks mentioning 4x6 coops....why not go 4x8 and use a sheet of standard sized plywood more efficiently?
Definitely have some good ventilation.
Great suggestion by valentinebaby on raising your coop but
I will suggest another 1/2 foot. With your original 5' height and then adding another 1 1/2' that would give your roof edge a finished height of around 6 1/2 feet. Unless you or your DH are very tall, by raising the roof this much neither of you should have problems bumping your head on the roof (metal/wood edges hurt!) as you near the coop. You could also extend the roof overhang a bit more without causing "stoop at the coop" fatigue.
Looking at the link to the Amish coop, the slope of the roof looks will drain rainwater on you if you must do maintenance in the rain...might it be better to slope the roof away from the door? You could put a small window in the door. Also, if you extended the roof out over the nestboxes it would protect you somewhat from rain and also protect the nestboxes themselves.
The two windows in each end appear to be fixed and non-opening. The roost appears to run between these two windows. Should these two windows be modified to open then in the summer time a draft would be created between them that would basically travel along the roost level which should be fine. In winter, though, this draft would be a no-no. I still would want to be able to open them during warm weather but I would think a narrow ventilation area placed around the roof/wall junction would work much better during the winter...and would help add to the ventilation effect in the summer. Follow patandchickens lead and delve into the wonderful world of plexiglas.
Windows could actually be made of 1/2 hardware cloth, fake mutin bars could be installed on the outside of the wire to simulate window panes....in the winter pre-cut pieces of plexiglas predrilled with mounting holes in the corners and weather-stripping attached could be installed with thumbscrews.
Lot's of modifications you can do...have fun!
Just some thoughts...
Ed