Sorry this message turned out to be so verbose.
For whoever has read this far, I'd greatly appreciate any feedback!
-- F.
Not so much.
[1] Instead of reading from an external file, think in having it as a
message.
[2] Your extension will have holes. You won't be able to prevent doing
{{subst:Approved}} to a page, if you hook before substing, they can and
will still copy & paste the template content.