That's a good point. I often store stuff in the enclosed so being able to get in there would be nice.
For the doors, I have the 12'H door on the left planned for RV's.
Looking at your diagrams I would:
1. See about raising the ceiling so that you can fit a 14' tall door (even if you don't install that tall of a door now) that way you "future proof" against taller trailers in the future
2. When you lay your tubes in the floor, lay them out to allow a lift in each bay (either a 2 post of a 4 post), that way you can add another lift or two if you want to down the road.
3. Which way will your roof pitch? Can you have it so the doors are on the gable side? Otherwise you will end up with piles of snow/ice in front of the doors when the roof unloads
4. When grading, having 1-2x the depth of your shop be flat (or close to it) and graveled so you can unload a trailer into a bay without needing to jackknife the tow vehicle makes life a lot easier (looks like you have that?)
5. On the overhead hoist, would a forklift with a boom on the forks do what you want for lifting engines and such? If so, I would get a forklift (or at least a walk behind power drive "stacker" straddle type lift), doesn't take up much space and it will likely be the most used item in your shop.
Something like this:
having spent way too much time in a shop with all the doors on one wall, add another even if its a man door to the back of the building. it will help you get a breeze when opened.
Best part of my 30x40 shop is, two 11h 12w doors on the front and one in the back.
Open a front door and the back door and you get a cross breeze.
start the slope for the doors inside so to help keep any buildup on the doors from coming in.
Also a good idea, doesn't have to be much, just enough to have the first 8-12" have 1/8" to 1/4" of drop.
Aaron Z