*As far as I know* there shouldn't be any probelms with you moving them over into the file system as long as your server is not running in safe mode. I know
vB has quite a few checks in there when changing the storage method, so I don't think you would even be able to move them if there was going to be some kind of a problem. It really is better to store them as files anyways since they don't take up space in your database then.