How about Miraheze provides a library of templates for Miraheze wikis to make use of? It could be forked from en.wikipedia. Over at Wikia they have implemented a Templates Wiki.
For full functionality MW should ship with templates bundled in or there could be a central repository (like commons does for images) but there is no sign of this happening any time soon. Miraheze wiki admins either write their own templates or export them from elsewhere e.g. en. There is much duplication of effort. Templates are a headache to understand, install and maintain. Miraheze already makes life considerably easier for wiki admins, allowing them to focus on adding content instead of diverting time and energy to keeping up with the upgrade-debug race - template inclusion would enhance this.