Well, one thing for sure.......
You have enough people wrapping their vehicles that its caused your local codes and inspector people to become concerned.
Either you have a lot of eye sores down there creating this neighborhood concern to start regulating it..... or business is booming in this field.
Like Fred said... to be fair, it will have to include ALL types of lettering and techniques, so it's only a matter of time before buses, large trucks and other types of vehicles start creating a codes area for getting this service done, but until then.... try to change your inspector's mind by telling him it will greatly effect your business if they start getting permits for these things, also. I remember not so long ago when you didn't have to get permits for lettering windows.... or even walls. First one borough or city does it and then it spreads like wildfire throughout the region. Yuck !!