Doubletrouble, you are little bit exaggerating the problem.
Usually the motor boat law says that registry needed is only when power over 11kw, if below it’s not needed . the numbers could differ of course in different countries, but nobody is registering toys, tiny engines of power SUPs, toy RC boats etc. The boost weak engine falls under that category.
Even big Jetsurf falls in the category UNDER 11 KW.
Of course the user with the “boost” will not be welcomed in the lineup of pro surfers, but if you have a surf school where they teach casual surfers to have some fun on the small day and they all use it, it will help them a lot stand up faster.
Wavejet failed because their price tag was ridiculous 4500 for super weak propulsion and heavy board and i think they had some patent issues too so they moved to kayaks