Oh, Now I'm torn!
Compare and contrast...
Common stages: Prefabricate a new base in quarters. (I think doing it in quarter sections pre-empts next time it rots.) : Clear the immediate perimeter of the shed of soil/rubbish.
Empty the shed : Apply Plan A or Plan B : Refill and Paint it afterwards.
Plan A
Cut a line about 6 inches inside the walls so the rotten walls will be resting on a strip of rotten floor.
Attach stilts to the most rotten long side.
Jack that side up by 3 inches. Let the shed creak and tilt.
Remove that part's attached bit of rotten floor.
Repair the bottom of that wall, while it hangs there.
Lower that wall onto temp timber that is as thick as the base was. No intention of doing anything to fix the floor yet.
Do same on each rotten wall in turn, until we have repaired walls all resting on timber, but with stilts still fixed to outside of each wall.
By now central remaining part of floor can be removed. Then we have a repaired shed with no floor but concrete slabs below and a perimeter of timber.
Sweep the slabs.
Raise the stilts once more.
Put the new floor in place of the temp timber 'footings.
Lower the walls and attach to the new floor.
Bonus stage. Raise the whole shed with floor by about 6 inches.
Push sacrificial bearers or even whole pallets under to keep the shed off the ground.
Remove the stilts. Fill any screw-holes.
Paint the shed in situ.
If weather turns bad, shove everything back in the shed temporarily, whatever state it's in.
Plan B
Remove rather quirky glazing.
Remove nailed down plastic roof.
Dismantle the shed into its four walls, roof and rotten floor. Lay them out.
Replace floor, with one pre-fabricated.
Repair all panels at one session.
Paint all panels while laid out.
Reassemble walls to floor.
Replace roof, almost certainly with new plastic sheets.
Reglaze.
Advantages/disadvantages of Plan A
*Can be paused at any time and stuff can be put back in.
*Less time needed for dismantling/re-assembling
No need to damage and repair the roof.
No need to mess with the glazing.
No need to maul whole side panels back into place.
Max comedy value.
But...
Repairing hanging sides will be a faff.
Painting the assembled shed will be a bit awkward.
Stilt holes will need filling.
Advantages/disadvantages of Plan B
Panels laid out will be more accessible for better repair.
Easier to paint as separate panels.
A cleaner solution, less of a faff.
No need to repair stilt fixing holes.
But...
Time and effort of dismantling and re-assembling.
Can't be paused if rain stops play.
Re-fixing the roof will be a PITA.
Reglazing will be fiddly.
Less comedy value.
I suppose the only way to know will be to try Plan A and see how well the first, worst, side repair goes. Maybe the jacking up process will just cause it all to collapse in a heap.
