Ill see if i can get a pic of my brothers shop. its 30wide x50(deep) 2 car door on the front off to the side. Front area has desk/paperwork/books etc. Also clean stuff, building supplier, electronic junk, fridge etc.. At the far back there is 2 rooms inside the main room, the top loft is for storage, of big bulky items. Its sturdy so the limit is pretty much what you can put up there. Inside the rooms, the one is the machine room, lathe, drill press, moving to the front corner and out of the room is welders/welding table etc. Other room has furnace and storage shelves for supplies. The machine room and be walled off with a curtain to heat just that in the winter (NY) the wood furnace heats it very nicely after a 6-8hr warm up from dead cold.. Ill find a pic...
More space is nice, but more space = more junk - so keep organization in mind. I've had good luck with ebay and craigslist for cabinets and storage stuff. Its made a world of difference in my small 2 car garage..
saw your last questions - my brothers is on an Alaskan slab with block walls on the 2 back sides that are set in to the bank.
drive through - unless needed for access out back I wouldn't simply because doors are not as insulated as walls. I think a well placed door can provide access to all the work areas needed.