Wikimedia Bugzilla is closed!

Is it possible to create a system message allowing to customize the toolbar like [[MediaWiki:Sidebar]] ? Indeed many Wikimedia sites add some extra buttons with JavaScript. It would be better for accessibilty (by reducing the JavaScript hacks). The message could have this syntax:

* Tip (description)
** image (either in $imageFiles of MessagesEn.php either the URI)
** open
** close
** sample
** accesskey
** CSS id (or automatic)
* Bold text
** button-bold
** '''
** '''
** Bold text
** B
** (mw-editbutton-)bold

With a single line for each star, using \n if needed. There is perhaps some better syntax. I think the only major change would be the reading of this message, but it already exists in part for the sidebar. I don't know good caching methods, but perhaps it could be better to cache the interpreted text (like the sidebar ?).