River valley biome variants / river improvements

the idea is to, instead of having awkward green stripes in mountainous / desert biome with no water in sight, there is a gradually flattening river valley before a river. Currently rivers are usually impossible to traverse more than 100 blocks due to traveling on uneven terrain, and they also get extremely shallows at points. River valleys will be on the edge between every biome (except oceans) and river biomes that act as a way for the land to be deeper so rivers can go deeper and should always be flowing and not blocked in any way, shape or form. And villages should spawn much closer to rivers in the style of the valley variant they're in.