I had a 8' by 6' shed with a rotting floor..
.. and a bit of gentle lifting revealed that the walls were not nailed to the floor..
So I took the roof panels off, then tipped the shed over onto its side.
Would that give you a wall that had temporarily become a ceiling, and could then be worked on? [your rotting wall having in effect done a 'garage-door' type manouvre]
'Assembly is the reverse of disassembly', etc.
You could also deal with the brambles, triffids, etc while the shed superstructure is resting on its side, out of the way??
ETA: cross-post with Tiermat, and similar strategy!