I can imagine other interesting use cases. fat32 over the network, for example: so you can e.g. plug in a USB device into some legacy hardware, and when it does a directory read, the device lies to the host about what's inside, only retrieving the bytes over the air during a file read operation.

I think the hard part is that if the "disk" is mounted, the FAT would be in memory on Windows, so it's very hard to put in a file from "outside", because Windows will probably never re-read the FAT from the disk and will never see that file.