Well, people can ride pedal bikes at unsafe speeds on MUPs ... so maybe there needs to be a ban on those too?

I can walk off the MUP, grab a tree branch, and walk back onto the MUP and beat people with the branch---do we ban branches, or walking?

If the MUP needs more law enforcement the answer is more law enforcement.

All laws are basically suggestions ---like speed limits---which can be enforced, but mostly people are expected to follow the rules, keeping in mind the greater good and the benefit each individual gains as part of the greater whole.

For instance, most people don't steal. The law, the moral training, the understanding that if theft is widespread, no one--not even thieves---are safe from theft---keep people from stealing. But some people do steal.

Some people will operate Any vehicle in an unsafe manner and endanger others without consideration. Skateboards, pedal bikes, electric bikes ... idiots with double-wide baby strollers are huge hazards on MUPs, but even worse are people on foot who are physically on the MUP but in actuality are ins some other realm, lost on their phones or music players, cut off by their earbuds.

Should we ban music? Phones? How to enforce that, since we can't even keep people from texting while driving?

Make whatever safety rules you like. Most people will stay safe and not endanger others simply out of common sense and basic decency, and some people, lacking both, will be hazards no matter what.

What about people who challenge rules? Well ... what are we doing about them now? It's not like e-bike Create those people. You say yourself there will always be such people which means they already are. So what do we do now?