Not sure about converting into a low floor. I would think that it would not be possible seeing how our slf bus is constructed. I like the idea of raising a roof area and making a loft
and still be low.
The transit low floor buses are pretty cheap. We paid $5K for ours with was a good price because it has been running great.
The gillig low floor mostly go for scrap prices. Don't worry about the inspection because it says very little about the engine / tranny and rust issues and more about the safety features, lights, brakes, emergency equipment. All stuff that can be fixed or is obsolete in your build.
If you buy one look for an auction that sells more at the same time because they are buying new ones and not because they just want to get rid of one worn out unit.