Not exactly applicable to your needs, but here's what I did at my old 1954 cottage in California:
It had a glassed in patio behind the house that was added on decades ago. That had 4'x8' glass panels between 4x4 posts. The floor was a patchwork of concrete mixed in multiple batches and only about 2" thick. Probably made over time using bagged concrete mix. It was **** ugly. The roof had one end resting on the existing main house roof, with roll roofing tied to the main gabled roof. The eaves at the rear were about 2' long, and were just extended rafters. the rafters were 2x4s on 16" centers.
So, one of the glass panels got broken. I decided to convert the whole thing into a second bedroom for the house. To avoid having to permit it, I treated it as a "repair to an existing structure."
First step was to figure out how to raise the far end of that shed-type roof, enough to demo the entire structure, but re-use the existing roof, which had recently been re-roofed, along with the whole house.
What I did was install two 6x6 posts outside of the structure. They were on concrete pillars, and braced in all directions with 2x6 angled braces connected to the 6x6 posts and 4x4 buried posts farther out. The 2x6 braces were attached to the posts with 1/2" lag screws.
Then, I put a 20 foot long 4x12 beam across the two 6x6 posts about 12" out under the extended rafters, which were cut to allow for that beam and two 4-ton bottle jacks. Little by little, I jacked up the roof. cutting nails as they were exposed. Once the roof was off the back end of the structure about 3", I added a couple of 2x6 pieces from the outside of the 6x6 posts to reach up to the 4x12, lagging them into place to ensure that the roof couldn't move down if the jacks failed.
Then I demolished the entire old structure and the poorly made floor. I formed up for a new 3.5" slab, with 12" x 12" footers and 10x10x6x6 steel mesh and poured and finished a new slab. Once that had cured, I framed up the walls for the new bedroom, building them to match the original slope of the roof. Windows and an exterior door were also framed at the same time. Once that was done, I removed the safety stops and lowered the old roof onto the new framing, installing ties, etc. for the rafters to the new frame. I got rid of all the framing for the roof lift stuff and stored that 4x12 beam for another project. I finished the interior and exterior of the new bedroom to match the rest of the house, which was rustic looking stucco.
It all came out fine, and never got noticed by the assessor, since it did not change the footprint of the existing house. Everything was done with excessive attention to the risks of working under a propped up roof. A guy can do almost anything with enough planning and preparation. Even stuff you probably shouldn't do. Just overdo the safety aspects to give yourself plenty of margin for problems.
