I have a confession to make: my chicken coop is a very "substantial" and practical building but it isn't very attractive

. It has lasted virtually unchanged for nearly 15 years and I don't think it will look different (or better) after another 15 years.
I was thinking of replacing it a couple of years ago but know how it would go . . . I'd have TWO coops in a too small backyard because I couldn't bring myself to get rid of the 1st one!
I found people online who built
greenroof coops - entertained the idea for awhile. A
waterproof membrane against the roof deck is required. It can be vinyl as might be used on a balcony. Some folks used a
pool liner and that could probably be easily found at most garden centers. I did notice just going back and checking this morning that the people who used
2 sheets of 6mil plastic got rid of their chickens and coop 2 years after they'd built the coop but don't know if the roofing material had anything to do with it.
The growing media should be light, light, light since it has to hold water which is heavy, heavy, heavy :/. I think you might want to really shop around for good-quality, fertile stuff and then mix it with about 50% perlite. Perlite is about the lightest ingredient you could use that would hold water well but it has zero plant nutrients.
. . . just a few thoughts. It sounds like you have a very worthwhile project ahead of you

.
Steve