I mean... you can literally do that now. You can set up a loop to iteratively pentest, review and patch a codebase (with human supervision as you prefer) and it'll find and fix more vulnerabilities in a day than a pentest team used to find in a quarter, for a tiny fraction of the price.

This isn't a joke, this is now part of my pre-launch SOP. I even have it tracking everything so I can log stuff to fix vs. known shippables vs intentional design/false positives vs. upstream stuff which doesn't have a fix available yet, and keep track of which builds have the fixes. Almost entirely automated, I mostly review the findings and do some categorization/enrichment during the pentest review stage, and do a human code review pass as patches are submitted.

Stuff that used to take me multiple hours to write a fix for and then weeks to get code reviewed and deployed now get done in minutes.