And then we will use this template at the bottom of every single page, whenever we do one of these overhauls?
Because this is going to become an expected part of every single page, we won't need to do it at the top (where it is obtrusive). Anyone interested can check at the bottom of the article to see when a substantive (meaning-changing) edit happened.

This will be good. readers won't have to sift through "simplified the language" edits in the page history to figure out if anything substantive has changed since the last time they studied it.

Something like a script that requests a list of pages once every 3 months with ?action=purge -- schedules via Cron or some such thing, for the middle of the night?