Currently the installer attempts to fake systems in core, like the cache, and actually duplicates a lot of code found elsewhere for module management and what not. Why not simply package a minimal database dump, similar to how the update tests used a Drupal 6 dump written in DBTNG, that can be installed to create an extremely minimal Drupal installation. At that point the installer can act like any other module and provide forms to complete the process.
Taking it old school, but +1.
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