Clearly, but by entangling so many aspects at once you've made it a reckless maneuver to try and contribute ANY patch until such time as this one is landed.  If I work from 2.1, my changes WILL conflict with yours.  If I work from this branch, I cannot go from working code to working code and so I can't even be reasonably confident my patch is adequate.

A better approach would have been to start hoisting the bodies of rake tasks into modules/classes, making the actual tasks be stub calls.  Land that, then proceed with the scaffolding issue.  Land that and proceed with the plugin installation fix ups.  Land that and the  proceed with a pure-gem usage mode.