Tyron and the VS team recently released a general outline of future plans and they're taking in a lot of community feedback. For the next update (which is focusing on a combat overhaul), they're actively working with a skilled modder named Malteiz, and have incorporated modded features before, which is a good sign that rivers are on the horizon due to modder 'sneezerstein' already creating a mod that adds just that. It's called "Rivers" and is one of the most popular worldgen mods in general, and it'd def be up your alley until it's officially implemented :)