[Cathar]

No motors. Some angle on the edges of the slits would be enough to provide rotational motion as the water passes through.

Scimitar. Best way to describe it is to ask you to picture what shape a slit would have to be if it were of fixed width but has to provide a fixed time unit of opening when the disc rotates across the range of radii.

I believe in the Formula 1 style of advancement philosophy. Explore the limits at the outer edges of practicality and affordability, and then decide what can be folded back into a commercialisable low-cost (but lower performing) product, but still have that low cost product benefitting from the advanced work.

Of course, if you build a Formula 1 car, everyone wants one though. $300 seems extreme, but in relative terms there'd be very few people who wouldn't at least consider buying a Formula 1 car if it only cost 4-6x as much as a sporty family sedan, even if the track times don't improve by a great deal...