Realistically you won't be inside the coop for THAT long, but I do go into mine 2-3 times a day (daily clean up in morning, making sure everyone is roosted in evenings) so that's enough that I don't want to be bent over to manage things.I guess I may have underestimated how often I'll actually be INSIDE the coop. All of the litter can be cleaned out from the outside. Yeah, it is a little short. I've been trying to figure out how to provide more ventilation, and because of the shortness, it's kind of hard to not have birds exposed to wind while on roost. I'll figure something out.
With what I was thinking for roosting perches, it would actually be pretty much IMPOSSIBLE to get inside the coop. Guess I better go back to re-thinking that. At this stage I'm not inclined to consider raising the height of the walls. They are all framed up and installed. Raising height would basically mean starting over.
Total open area of: 35+ square feet for 15 birds. Should be sufficient.
I can crawl under the platform well enough. It won't be fun, though. You're right about that.
For the roost, you can either make the bars removable for better access to clean out, or hinge the entire unit and lift it up and out of the way when you need access.
Re: ventilation, now that's a good amount of ventilation if you put all of that in. As you're in a warmer climate, more is definitely desirable.
For getting underneath the coop... you got any kids bigger than the little one in the photos? Send the kids under there! (But this is why I have the underside of my coop closed off... I lose some outdoor space that way but at least I'll never have to fish birds (or even wild rabbits, which used to hide down there(, out of there.)