Pretty much the consensus seems to be that idiots will always screw things up by being idiots, and reasonable people will always adapt.

If enough idiots screw things up badly enough, steps will be taken. We might see a rash of people coming off the trails on their E-MTBs to meet police, investigating based on video footage which seems to excessive speed (while the pedal-MTB crowd sits back looking innocent, hiding their cell phones, and trying not to laugh.)

Same on bike paths. I am sure someone could print a bunch of flyers and hand them to every one on the path saying "send an email to the city if you want better police patrolling for speeders on this MUP" and all it will take is two cops with radar guns on two Saturdays ..... bunch of ticket revenue for the PD, bunch of P-O'd Ebike maniacs fuming but not riding that MUP.

Or .... a guy at the path entrance with a sack of one-inch dowels labeled "spoke sticks" passing them out to all the silver-hairs and dog-walkers and stroller-pushers.