I was thinking about what I suggested a long time ago, here, about having a changelog with important changes. It would simply list versions chronologically and include “major changes”, especially breaking ones, for each version. Upgrading would then be reduced to pull up the changelog, start with your “from” version and go through everything until you reached the “to” version.
Having changelogs isn’t uncommon, the challenge in OHs case is how to “filter it down” to something manageable, because especially all the changes to the add-ons makes for a complete information-overload if everything from the current release notes were just put into a chronological document.