But, I am actually looking forward to a seamless integration mechanism where users won't have to modify existing Piwik tracking tags. Ideally Piwik tracker code would pull the plugin code. This may be possible by dynamically generating (and caching) piwik.js and including blocks of codes pre-registered by third-party plugins, right within piwik.js.
Hooks in piwik.js was implemented to facilitate unit testing. This will be reworked in #739.
Rolling into #739 by reference.