I'll 2nd, 3rd or 4th... get a 14 foot high door. Now is the time. The cost between 12 and 14 is not that much, yet doing something with it after is a big deal if a 5'er or class A ever comes.
You can see on mine I have a 12W x 14H camper bay. The 12' wide makes it no issues backing in. While 10' works, it can be threading the needle every time. I have that now parking at our house.
In my case the middle bay is a 12 foot high. I can put my present camper in the middle and may do a total camper rebuild or build a new one from the ground up in a few years and I have room to work on it.
My camper is 33 feet, bumper to ball. The building depth is 40' outside and I loose about 1 foot for the 6 x 6 poles. Yes I have to unhook, however the frontal length and space for my "stuff" was better served unhooking.
I agree, plan for natural light. Enough to see walking around at least. A translucent rear panel and glass in the doors works. More is always better.
Good luck and hope this helps.
John
