From all that you have said it seems FL its on its way to become another cali.......
Here in MN once you purchase a vehicle you NEVER have to take it anywhere for inspection even when you buy a vehicle from private seller, for example last year I bought and rebuilt crashed a jeep .
I did most of the work very slowly as a weekend project and when it came time to go to the DMV and title the vehicle all I had to present were receipts of the work(parts in my case) and I was good to go, from the sounds of it in FL I would have had to jump through a lot of hoops.
Also regarding the picture above there is a difference between mods being made for off road only vs a mod that will change the classification/title of your vehicle, if you argue that the Quad conversions are not street legal I would agree with you on the basis that they have never passed DOT testing and you could be stopped for that but not because it is no longer a motorcycle.
Just because your state has restrictive laws doesn't mean that every state is like that, another reason to always stay in the Yankee side .
I wish a few of the many people with Quads would speak up and shed some light into the debate, the guy with the quad that crashed on colorado last year is from FL, he would be a good source since he has had his quad for almost 2 years and drives it in the street and from FL to CO at least once and never posted of any issues.
The one quad that I know off locally is not part of the forum, he has had his for a year now and no issues here in MN/WI/SD.