The "Version check" part of this came up in today's "Reconnecting with the shared hosting community" IRC office hour. I created phab:T119121 "implement a version check". Some relevant bits from that meeting,
<legoktm> I'm rather interested in how shared hosting users upgrade (if they do at all), according to wikiapiary:Statistics 68.23 % of known wikis are using unsupported versions. And if people aren't upgrading to newer versions, they're not getting newer features, which seems like less of an incentive to stick with MW.
<legoktm> gilles: I suppose the next question is, are we doing a good job promoting our new features, and is that reaching shared hosting users? The installer has an option to subscribe to mediawiki-announce, but do shared hosting users get that option if they use a different installer?
<gilles> ... so they probably don't even know that they're running something outdated
<gilles> #idea find (better) ways to advertise new versions/new features to shared hosting users
<spagewmf> For updates and support, can we built into core MediaWii a parser tag <check_for_updates> and in the default install it is on the default Main_Page?
<Trela> spagewmf: Special:Version would be a good spot to have a "New Version Available" indicator for logged in admins.
<cscott> spagewmf: probably Special:CheckForUpdates would be better, with default permissions only viewable by admins
<spagewmf> cscott special page works too, and the default Main_Page can transclude {{Special:CheckForUpdates}}