I am afraid my perfect coop would closely resemble Ralphie's, so that's not much use to you. In terms of "can I afford this within the rest of my lifetime", I'd say I already have my dream coop. The floor, which is vinyl over pressure treated plywood, is raised far enough off the ground to see under. That eliminates hiding places for baddies, which was a major issue with my last coop. It has removable roosts, painted walls, an attic for storage, and a closet to keep the chickens from pooping on my tools. It has nice latches that lock when you swing the door into them. I can't think of anything else I would want in it—except more space. It's 12' x 12'. I'd really like a 20' x 15' or bigger so I could keep more birds over winter.
https://www.backyardchickens.com/gallery/albums/coop-build-2017.7428049/
What's the most useful for me is sections. Places to put birds that can't be together. I have movable pens already, but my dream coop would definitely be big enough for in-coop brooder areas. Until I get some bigger and more weatherproof separate housing, I have to make sure they can all live together in winters because the pens get entirely buried in snow. I don't know about you, but I refuse to do one more lick of shovelling than is entirely necessary to make it in and out of the house.
Get the chickens these and make them shovel their own paths like I do.
https://www.amazon.com/dp/B01JFF9ZM4/ref=nav_timeline_asin?_encoding=UTF8&psc=1