I run two drives, an SSD and an HDD on my computer. I have very limited space to hold files on my SSD, and since that is my OS drive, it is where my BeamNG mods go. I have over 4gb of BeamNG mods, and that space could be use a lot better, but I'm forced to keep my mods and cache in my documents folder. Allowing for the remapping of the BeamNG.drive folder from the documents would be super helpful for those of us trying to save space on our drives.
Or alternatively, you can set the documents folder to be on your D drive in windows. This way you won't need to set the path after updates, but all your documents will be on D.