Do we really need 'new' kit? The real problem is not speed, but the wash kicked up and its imact on the Broads environment.
We all have at least one 'Mk1 eyeball' which I suggest should be turned rearward at regular intervals to see what impact on the water your passage is making !
Of course, there are those boats, with 'deep v' hulls or other planing designs which will always create excessive wash at or within the speed limits. They do look the part though,apparently......
Hull design is the issue - perhaps a loading on the tolls of those types of boat, comensurate with the damage they are creating