Good news, it is now possible to mount USB media (including FAT formated) and network shares with drvfs on Windows 10:
Mount removable media: (e.g. D:)
$ sudo mkdir /mnt/d
$ sudo mount -t drvfs D: /mnt/d
To safely unmount
$ sudo umount /mnt/d
You can also mount network shares without smbfs:
$ sudo mount -t drvfs '\\server\share' /mnt/share
You need at least Build 16176 so you might have to opt-in to the Windows Insider programm and then update Windows. Source: