ref: https://www.youtube.com/watch?v=8a3r-cG8Wic

"The length of a S curve is about six times the width of a channel"

Seems like I'd have to completely re-implement water movement to handle this though.

I really like this idea, but I don't see how it can work without water travelling further and/or changes to the default worldgen. Closing for now. I'll re-open if something makes it possible. There already is some directional changes due to streams eroding to stone and water levels falling as edge blocks erode, perhaps it's good enough.