As much as I'd love to have this kind of additions, there are user interface related questions which are more or less unclear for me.
Let's imagine we would have brooks some 1 - 12 meter wide, criss-crossing the terrain. And you're travelling on the overland map. Would you like to get notified every time you automatically cross a brook? Or get zoomed-in every time? Or just simulate on a higher level, assuming that your character figures a way to cross the brook without asking player decisions? Or allow the player some setting or configuration to be switched based on need? For example, if you are thirsty, you'd probably like to be notified whenever your character spots a small brook?
Or, you are just covering a longer distance, travelling on the overland map, using the high-level simulation of automatically crossing brooks without interrupting your gameplay with constant notifications like "you cross the 23rd brook of the day, again". But then, that one time the simulation, RNG and skill checks would determine that when auto-crossing a brook you slip and fall. Now what? You then get zoomed-in into the situation?
(also, I have to say that adding small paths and brooks would require a lot of additional data to the world-map, to keep track on how these smaller-than-a-world-map-tile features go, something like "this tile is mainly forest of type X, but there is a brook running from north to south, and then there is also a east-west path", and should the data structure allow only one brook and one path per world map tile, or are the occasions we would need two creeks near each other? It would be an interesting coding task to inflate this data so that when you travel in the zoomed-in map these creeks and paths would run uninterrupted but with natural curves.)
I'm not saying these are reasons we won't implement these features. It is just to affirm that, like JP_Finn says, this would be a sizable change, requiring a lot of re-coding the map routines and re-structuring the entire map data structure.