Starting from this discussion http://www.mwusers.com/forums/showthread.php?p=33953 I posted a new extension into mediawiki extension section. It's a simple bridge to load markitUp editor and replace the default toolbar. The default toolbar is simple hided with a Jquery hide() function and no changes are made to the mediawiki core. The Jquery library is bundled with markitup package and is 1.2.3 version. I think that is an easy customizable and alternative editor.

The initial releases and the SVN repository is here http://code.google.com/p/markitup-mw/. If someone want to contribute to this extension feel free to email me and request a password for SVN account.

Best wishes