In general, I would favor less government regulation and allow market forces to determine the market. If someone wants to live in a park model built to whatever standard, I'd say that's their choice. If a municipality wants to tax that park model however it sees fit, then it's up to the affected to resist the assessments or move the trailer.
But there is one area that I can see where HUD may want to get involved and that is FHA loans. If you buy your park model with cash, then you can do whatever you want, but if FHA is lending money on your park model, then maybe they can have a say in the matter.