I just override required renderers, taglibs, html ui components and .js files, name packages same as with library (org.richfaces.*) so classloader loads overriden sources. Due to my overloaded jobs/issues, i haven't mavenized/jared the taglib yet. When i say "official version", i mean this improvement should be packaged - by RF and added as-is to library.
I simply jared only modified resources and added "historyRedisplayText", "historyAllText" and "historyLastText" attributes. so you must integrate them with remaining sources - and also dont forget to define these attributes on notify.tld.
As an opinion, also user should define severity based images and styles for history buttons. I dont know these features already available in RF 4.x, but they could be so cool.
Patch is here