The "Vesuvian Bespin" proposal here is that scientists have found high enough in the Vesuvian atmosphere, atmospheric pressure and temperature are potentially comfortable for humans to go without (or at least much less) extensive life support (ignoring chemistry problems mentioned below). So, Earth would be kind of the ideal place test such a construction before committing to going to Venus. If you want easier 'floating' (making certain assumptions about the technology one might use to do that, e.g. we haven't invented anti-gravity machines), you go down to denser atmosphere and trade off against ease of human habitability. Which would seem to defeat the purpose.
At about 55 kilometers (where it's close to 25 degrees C and maybe 2/3 of standard air pressure) there are clouds of sulfuric acid. I believe you can avoid them by going higher, but then you lose the appeal of having earthlike temperature and pressure.
