Above are some of the reasons I went with complete coverage -
Disclaimer - I wouldn't recommend doing this unless you're OK with heights, rigging, welding things you CAN'T break, having patience, and most of the other attributes members of GJ tend to exhibit
I built my roof solo over about a month, with the help of my old Case backhoe and several "helpers" I've fabbed as necessary, multiple comealongs, ladders, mag drill, jack stands, chain falls, etc - in retrospect, if I had it to do over I woulda probably gone with welded on angle and wood framing. Cheaper, faster, but probably NOT as modular/re-usable as the steel.
Mine is in 4 sections, a main one over the container and 3 8x12 modules that bolt together and can be separated and removed one at a time if/when necessary. There is NOTHING welded to the container - I'd do that part the same if done in wood, especially if I ever intended to re-sell the container.
With the exception of a few main framing tubes that're 1/4" wall, 90% or so is 2" square tube with .120" wall. At today's steel prices, the framing alone would run right at $1800. I wouldn't have done it this way EITHER, except future plans call for a different use of that space so everything, INCLUDING the 20' container, will eventually be moved ELSEWHERE so it would either get torn down or (because of the modular build) just "re-assembled" in a different spot.
Anyway, a few pics for the "masochistically inclined"
... Steve