1) The extension itself clearly still needs UX love. The filter UI is already cluttered, labels like "Users (Sep: |)" and confusing icon choices (magnify icon to expand links) don't help. 2) RecentChanges is a core feature. New extensions/features need to tie into it all the time. Maintaining an extension for some subset of wikis that choose it and ensuring its compatibility with all future code strikes me as needless complication of our core UI. In other words, if these improvements are worthwhile (and I'm not disputing they are! Credit to Niklas and the translatewiki.net folks for fixing issues in their workflow), I would argue that they should be made in MediaWiki core, and consistently applied across all wikis, ideally after some more UX attention.
Creating here without specific judgement.