I would like to see this work without any patches to core or especially provision.

I believe it's possible to support ITK or similar software without patching provision.

I also believe there can be a way to affect the Drupal bootstrap without patching core, maybe by changing the drush bootstrap process, or at least lobby to get that patch factored into core itself.

What else would be needed? I would like to see this be a regular drush contrib that could be promoted as a proper Aegir project. I, for one, need something like this, but I don't want it to be bound with Plesk. ;)