Hi,
I've written an RfC about moving most of the Echo extension code into MediaWiki core: https://www.mediawiki.org/wiki/Requests_for_comment/Notifications_in_core.
RobLa has written a summary of it on the Phab task: https://phabricator.wikimedia.org/T128351.
Feedback is appreciated. :)
-- Legoktm