Problem is that you can't change ground tiles dynamically. You can script to change placeables, like snowdrifts and herbs and trees, but you can't change a tile, or add and remove water within a script.... or at least any way that I know of.
You'd have to have two versions of an area, a "spring" and a "winter" version, which would mean physically changing them in the mod every 6 game months or so. A big PIA for the developers.
^this. Not worth switching out areas for something that will probably not see very much use
As a note, you can use a script to change the
appearance of a tile (such as putting lava over the ground or even water) but you can't make something walkable that isn't. Water tiles aren't walkable. Switching out areas manually every in-game winter (of which there are many in a real-world year) is just too much of a hassle to be worth it.
