Well, First, you might want to reconsider your use of the word 'should' all over that post... Perhaps changing 'should' to 'I wish' might come across as more palatable, as few people, especially burners, appreciate being told by anyone what should or should not be. Then again, maybe not.
Second, You seem to have a problem with art cars/party floats based on the noise issues in addition to the safety issues. However, I do have to refute your assumption that there are generators powering the sound systems. The few vehicles with large sound systems I managed to see up close all ran them off the engine of the vehicle -- the battery/alternator. In fact, many of the art cars I saw out there this year had no Big elaborate sound system at all, just a couple of speakers that pumped out about as much as standardly equipped car stereo would. There may have been sound systems out there that did require an additional power source, it is not hard to imagine that as the case. However, I would imagine that even so, those systems could not exceed the limitations imposed on any of the non-mobile systems.
Third, safety -- While I have no problems with the BMOrg holding art cars to a certain minimum level of safety, (EG having lights for night driving, working Breaks, working steering) we are all ultimately responsible for our OWN safety. If you feel a vehicle is unsafe, don't ride it. Kathy's very unfortunate death came from dismounting a vehicle in motion, not because of an inherent flaw in the design or any irresponsibility on the part of the driver. I for one am getting pretty tired of the cry for increased rules and regulations because something is not perfectly safe.
While I understand your lament for years past, when Art cars were just that -- modified cars that looked like something else, or had an artistic theme to them (the Toy car from '96 comes to mind), I am not certain that banning these so called party-floats is a good idea. Telling anyone how many folks they can and can not have in/on their vehicle is more imperialistic and paternalistic then even the current presidential administration, and does nothing to promote personal responsibility. Telling folks their idea of art is not valid and that because they do not agree with someone else's idea of art is just plain boorish.
One of my all time favorite Art Cars was "Barzilla" a green motorized Bar, complete with bar stools. It carried anywhere from 12-25 people, depending on how friendly they wanted to be, and was a centerpiece of the '98 and '99 incarnations of Gigsville. While I only got to ride it twice, I had some great experiences on it both parked and in motion. Perhaps it was a 'party float' as you say, but to a lot of folks it was something much much more. (Aside: I do not remember it having a sound system at all.)
Finally, I am not a big art car rider. I caught a ride on exactly one art-car this year, and it was to get from the Man to 3 O'clock/esplinade -- and that was technically cheating during the Skynyrd Marathon, cause I was pretty drunk, and thought it would be funny. It was.
I say if someone wants to assume the responsibility of creating a motorized party, let them. If they want huge sound system, they have the same limitations as any other sound system out there. And leave it up to the owner/driver of the vehicle to determine how many passengers is 'safe', not some arbitrary rule that does not take size, stability, engineering, or purpose into account. And just like anywhere else, personal responsibility is the key for the driver and the passengers.