> The USB Mass storage model is "all or nothing": it forces the gadget to abandon everything it's doing with the partition/fs as soon as it's plugged; and then rescan everything (for safety, database updates, etc.) when unpluggued.
> That is a problem that cannot be adressed with a new filesystem.
Why not? The reason the gadget needs to "abandon everything" is because none of the currently-used filesystems can handle concurrent access to the underlying device at the block level. But there are filesystems that are supposed to allow that, like http://en.wikipedia.org/wiki/Global_File_System