Good idea about being able to get a wheelbarrow under the doors which I had planned but it just made it too high for easy chicken access. I also have found that using deep litter, you don't completely empty the building that often so small bins aren't that bad to carry to the cart.
I was...
Does the coop have a human access door?
Does the roof slope toward the run or away?
to maximize space, external nest boxes give more space in the coop.
IMHO 40" is pretty high for the bottom of the coop. It will take much longer for them to learn how to go in and out.
How many chickens are you...