Well, the problem is that the different maps have different features which can't be moved. Changing farm types via savefile editing on PC can indeed change the farm type... but it often introduces glitches. This is illustrates that the maps weren't built to be able to be swapped out mid-game, so all the maps would need to be changed in order for this to work, bring them all in line with a basic template... which would still be wacky if you try to swap to the Riverlands map where half the map is taken up by water. What happens to your barn when you change to the Riverlands and it is suddenly in the middle of a river? You'd have to ALSO have the in game means to rearrange every building on the farm as part of the process. This looks really complicated... a really big ask considering we've been told that this version of SDV is basically the final form, with very little coming in 1.6 that isn't just making it easier for modders.