saying words to the effect 'You better have a matching set of files'.

I agree.  And my point is that a user cannot know if the files are in
fact "matching" unless you specify actual information about the files
used to build.  A random version string like "7.0.0" is not enough to
technically verify.  A checksum (ideal), a file size (good enough in
practice), something that is specific to the actual content is needed.
Otherwise it's just a guess.

Regarding the name: I like unicode-letters.def.

thanks,
karl