Is it possible to create an installation pack in Drush make?
I have code to generate an installation profile from an existing site; it is still a work-in-progress in the issue queue here: http://drupal.org/node/1368242.  Presently it works with D7, but does not yet generate the necessary installation scripts for D6.  It still does a lot of useful work for you, though, and is a good place to start.

However, if your goal is to upgrade your D6 site to D7, what you are really looking for is Drush Site Upgrade.