I think the auto-tagging feature that I wrote a while back might fit into this discussion. It's a framework that allows you to attach rules to a directory level. A simple example would be tagging all media under your "movies" folder as a movie, and all that contained "720p" in the filename as 720P HD. The matching rules support regular expressions, and custom rule types can be added by adding a class that implements the rule interface. (I mention that because it is one way golgoj4's more sophisticated rules mentioned in the OP could be added, and only applied to a certain level of your hierarchy if desired - e.g., under 'tv shows')
There are a couple screenshots of the webadmin interface here: http://forum.linuxmce.org/index.php?topic=7116.msg50212#msg50212
. The patch is in trac, but was created against an early version of 0810 alpha, so it might require some tweaking to apply at this point. I just thought I'd bring it up in case it applied to what you guys were thinking about here.