I really think the maintenance part of it is going to be the downfall. Are you really able and willing to regularly lug up loads of bedding? Going up there daily in all sorts of weather to clean out, bring up food, fetch eggs?
But would the raised structure be a complete coop, or just a sleeping place?
Food, water, and nestboxes could be at ground level, if the chickens are always free to come out of the coop at will.
And if the coop is ONLY for sleeping, then of course the chickens will poop while sleeping, but they won't track is around much. So it might work to just spread newspapers or cardboard on the floor, let it pile up, and remove the whole mess once or twice a year. (Probably only feasible if the climate is dry enough and the ventilation is good enough for each night's poop to dry before the next night.)
Skipping some the of the walls is an interesting idea. Given my northern location with sub freezing weather I think I will need a completely enclosed and insulated coop.
Or maybe build something sort-of like a gazebo or covered porch: posts with a roof on top. Make the posts climb-proof, and let the chickens use the rafters as roosts. That way they could sleep 6+ feet up, could fly up and down, the poop could fall all the way to the ground where it's easy to clean up. If the chickens are up inside the roof structure, they are protected from the top and the sides, so it's probably good enough even in most cold climates.
And then put the food, water, and nests somewhere nearby but not underneath the roosts, because you don't want predators using them to get up to where the chickens are sleeping. But everything could be at ground level for easy tending, and you'd only need a ladder if you want to grab chickens off the roosts at night.