Russ Cox has posted a video tour of the Acme editor. If I weren’t using (and extraordinarily happy with) Emacs, this is the editor I would be using. For a long time it was only available with Plan 9 but Cox missed it so much when he stopped working on Plan 9 that he ported it and much of the Plan 9 environment to Unix like systems (such as FreeBSD, Linux, and OS X). That port is available to all as Plan 9 from User Space.
The video is entertaining and well worth a look. Perhaps it will give you some ideas that you will want to port to Emacs.