Whist messing around with accessing/using video ram in userspace, I stumbled across this https://github.com/Overv/vramfs
why not put some of that VRAM in your graphics card to work?
vramfs is a utility that uses the FUSE library to create a file system in VRAM. The idea is pretty much the same as a ramdisk, except that it uses the video RAM of a discrete graphics card to store files.
Disappointingly however is that vram is slower than tmpfs, around a third of the speed (all honestly I had expected it to have been faster).
But still interesting none the less. Conceptually at least, haven't actually tried it, you might be able to load/run Fatdog into/from vram.