Using a recycled vehicle wheel to anchor your footer sounds like it would work but I would use a 5 foot length of drill pipe welded to a round plate for the wheel end and a square plate at the top to match corner fittings of the container.
Spraying the wheel and pipe after welding with underbody coating to prevent rust and possibly using ready mix concrete to prevent direct soil contact and prevent uneven sinking as the anchor is placed under weight of the container.
Only bury 4' of the anchor and if you have not leveled the site from the highest point on the lot bury one anchor with a 1' clearance above ground and use a laser level or water level to place the other anchors at the overall height they need to be.
Using a tractor mounted Auger? if your wheel diameter is slightly less that the auger this could be a quick and easy operation to dig the holes.
I am considering using 2 ea 40' and 2 ea 20' to build a house I would use the same post and anchor footing system as your idea and I would have a 20' x 24' courtyard in the middle. the corners sections of the roof can be factory assembled as they would fit on a standard flatbed trailer
