I have done some work to start of rewriting the Drupal installer to be its own Symfony micro-app rather than a pile of workarounds upon hacks upon hacks. I do not have time to carry it forward, but this is a very important free-standing task to help clean up Drupal 8. It's also a great opportunity to learn more about Symfony, and become a Drupal hero for making the installer not suck. :-) It can also serve as an example for update.php and cron.php.
I don't have time to carry the patch myself, but I can review/help/assist someone else who's taking point on it. See the issue for details, or contact me (Crell) in IRC.