Shipping container as a shop? The craziest thing I've ever heard.....Who wants a 12" lathe, powerfeed drill press, turret (Bridgeport pattern) mill, horizontal bandsaw, 6x12 surface grinder, hydraulic press, tool cabinets, upright compressor airlines inside with bulkhead fittings outside, a 240v 3ph genset outside ran machines, four 4' 2 LED fluorescent fixtures with 110v bell boxes outside.......
Well, that was in a 40' - transported job to job by the contractor who built and installed the entire battery assembly line at Tesla in Reno. The components were built offsite, modifications and one-offs done right inside there.
Compact yes, but not uncomfortable. Beside an entry door, only real alteration was external roll-up door on one end. That allowed longer material in the bandsaw. To me, entry door was superfluous, complicating work floor layout, plumbing & electrics. Most can't build 320 square feet of secure rain tight solid floor for $2300. Make sure you paint interior white before starting inside.