The problem with that is that it won't work unless it is in a container that allows the editing of metadata with a re-save.
If I add things like an MPEG1 or MPEG2 video file to iTunes, I can add a bunch of metadata to it, like artist or album or whatnot, that doesn't actually get stored in the video file directly, but in the iTunes database.
Some tags, however, seem to be locked out - Season, Episode #, things like that. I think the solution isn't getting into the video file and editing metadata there, but figuring out how to get iTunes to let us to those "other" tags.
Thought, there might be a way to do it directly to the file. I know that under Tiger, through Spotlight, metadata can be added to ANYTHING, even totally new user-created tags - it is just that, outside of the Terminal, there's no means yet for your average user to get to it. I wonder if you could get into the Terminal and see the tags that iTunes is using, or add those tags and have iTunes read them.
I guess the first question as to which route to go would be, simply, for things like Video Type, Season, Episode #, etc., how is iTunes dealing with that data? If it is part of an iTunes database, a solution needs to go along that route. If it is using information available outside of iTunes, then that is the route we need to look into.