Requests for comment/A central repository for templates and other bits and pieces

Background
Other MW wikis templates are either written from scratch or exported from Wikipedia.

Problem

 * Non-WMF wiki administrators are having to debug templates, and struggle to keep them up to date. This is an extra level in difficulty from just install MW, configure and then add extensions.
 * Wikipedia specific features and images are sometimes included in other wikis.

Proposal
There should be a common repository for templates and other bits and pieces such as CSS and JavaScript.