Allow me to be blunt, I think asking for a water-park filled with just water rides (Log flumes, water coasters (like the Intamin kind), river rapids, and likewise) is a bit..impossible, considering the odds.
I think, if we'd ever see a water-based attraction, it wouldn't be what would be expected for a theme park. And to be honest, I'd think that'd be more niche than a boutique theme park.
What I think would be a good goal, is to make a water-park that can be done all day, and that it can be something that doesn't feel like a generic water-park, or hell, even water parks like Vol, Aquatica, and the WDW water parks.
I think, they need to find the balance, to make something that can be completely immersive and inclusive, while also offering a variety of attractions for everyone in the family. Hell, maybe even something that may be of a different take of a lazy river, to where it has slide-elements embedded within the lazy river, to get people from one area to another, almost like what Wild Wadi has in Dubai would be different enough from the rest.