New skins system

Right now, MediaWiki isn't a great place for skins:
 * we have a few 'official' skins released in the tarballs, but don't really have the resources to support many of them, and have no real process for adding (or removing) skins from this state;
 * installing a new skin, like a new extension, requires filesystem access, which excludes / unnecessarily makes life harder for some of our re-users; and
 * contributing a new skin is essentially impossible except for those of us in the ivory tower of the Wikimedia Foundation.

This means that almost every MediaWiki install out there looks a lot like Wikimedia sites

Skin installation magic
In the magic future, it would be nice for MediaWiki to have a proper skins system - that is, something more like WordPress or Drupal, where system administrators can browse and select skins through the interface and trigger a click-to-download-and-install process.

Obvious issues

 * Who's going to write this?
 * Is this just going to expand the confusion?

Technical issues

 * If we have a magic centralised gallery of skins, where will this be hosted? How will we run that? Magically within MWwiki somehow? etc.
 * Some of our existing 'official' skins have very deep integration or shared/semi-shared code - how would this work? Would we need to re-work them all to
 * Making this easy whilst the rest of LocalSettings.php isn't adjustable through the wiki would confuse some sysadmins; are we prioritising the right things to simplify?

MediaWiki tarball skin review
We should review which skins are packaged by default in the tarball. What would be most useful for our tarball consumers? Do they all actually want to look like Wikipedia anyway? How do we know what they want? Is posting to mediawiki-l enough?

Wikimedia cluster skin review
We should review which skins are available on the WMF sites (if WMF doesn't have the resources to support the skin and no-one offers to keep it current, we can't keep it on the site breaking things). To understand what we want from where, we need to get some data (proposed query):


 * For each WMF-hosted public wiki;
 * … grouped by bucket of user {editor; sysop; total edits > 100; total edits > 1,000; total edits > 10,000 };
 * … filtered by being active (account touched?) in the past {1, 3, and 12 months};
 * … how many accounts are set to use each skin?

Ideally then bucketed by similar-enough wikis so we don't have to review 800 independently (ultimately we have to come up with one decision for all wikis).

Also, it's been proposed to support lovers of the particularly-archaïc wiki skins to translate these into user-space CSS and JS hacks to run on top of a supported skin (e.g. Vector) - how plausible is this? How much does the software behaviour change between different skins? Does SkinLegacy.php do that much for people?