right now I was able to configure a DirEntry command to automount the target as the mountpoint directory is entered: it would be awesome if that could work with bookmarks pointing to subdirectories of that DirEntry folder, something like this
autocmd DirEnter /etc/**/* !mount /dev/sda1 /mnt/disk
/mnt/disk/folder1
bmark folder1
would mount sda1 when entering the bookmark folder1