Steven, I know that you plan to add support for videos in MB, but there is one idea about this that you may implement very easily.
1. Could you allow to add to MB library files of *any* type? Of course, if someone adds *folder* then only supported file types should be imported. And of course, all tags can be stored only in MB cache for unsupported types.
2. For unsupported file types 'play now' action must use external player automatically.
P.S. I guess that this small improvement may be useful not only for videos, but in many other scenarios also. In fact after implementing this request no other media file organizer except for MB will be needed.
P.P.S. This is not very important for me, but still may be useful: may be MB can launch one of several external players depending upon file type?