The whole discussion about Babel templates or even other templates includable through an extension essentially is about "shared content". Shared content that should be the same on every wiki but is separately and redundantly stored on every single wiki. That's comparable to images, which where stored separately on every single wiki until the creation of Commons. Or comparable to interwikies, which are stored separately on every wiki until today (although recently there were an solution proposed for this, see http://meta.wikimedia.org/wiki/A_newer_look_at_the_interwiki_link).
How about creating a wiki from which every Wikimedia project can include any pages. Like templates or interwiki tables or pages like info on legal contact addresses or the designted agent or help pages which could be useful to several projects (for example http://en.wikipedia.org/wiki/Help:Template which is synchronized with the master help page at Meta by bot).
This feature is already implemented in MediaWiki: $wgEnableScaryTranscluding (http://www.mediawiki.org/wiki/Manual:$wgEnableScaryTranscluding).
Well, the name makes it clear: This pre-existing functionality in its current technical design is "scary", but we could easily adjust the existing solutions (http://www.mediawiki.org/wiki/Extension:Interlanguage, http://www.mediawiki.org/wiki/Extension:Babel) to create a less "scary" technical solution to include all kinds of content from an central repository.
Marcus Buck