Here is my own take on Video Meta data and it is actually based on the "type" each is.
Yes, I agree that establishing that any type of file can theoretically relate to a "movie" is important. You mentioned ISOs which aren't actually video. This highlights the difficulties inherent in limiting organisational structure to "file type"...
The suggestion I proposed would take this into account to an extent - you can create any custom fields to establish whether what you're talking about is a "movie" or not. Or if you prefer you could use the [Media Subtype] field to select "movie".
I use two Type fields: [Type 1] & [Type 2] , which establish the medium that the file belongs to. These two fields underly my
entire database structure, and I've found you can organise pretty much anything (see below) this way. This is completely independent of file type and media subtype (which I don't use).
[Type 1] is very broad, [Type 2] is much more specific...
[Type 1] ... [Type 2]
Music... Album, Single, Compilation, Charts, Classical Album, Film Soundtrack, TV Soundtrack, Game Soundtrack, Music Video, Concert, Sheet Music, Misc Tracks
Film... Feature Film, Short Film, Trailer, Posters, Special Features, Scripts
TV... TV Episode, Trailer, Poster, Special Features
Theatre... Concerts, Live Theatre, Scripts
Game... Roms, Game Footage, Cinematic Scenes, Trailers, Game Art, Screenshots
Comedy... Stand-up, Comedy Album
Artwork... Classic Art, Digital Art, Photography
General Interest... Funny Pictures, Video Clips, Instructional Videos, Lectures
Print... Calendars, Art Books, Comics, Fiction, Non-Fiction, Magazine, Scripts, Poetry
Personal... Photos, Home Videos, Articles, Academic Records, Birth Certificates, Census Records, Service Records, Memorabilia etc etc
Notice that
1. many Types transcend file type
2. files can belong to more than one [Type 1] and more than one [Type 2]
3. [Type 2] values can belong than more to one [Type 1]