I built something like this that we use both for migrations and disallowing new instances of bad patterns for my mid sized tech company and maintain it. Ours is basically a configuration layer, a metrics script which primarily uses ripgrep to search for matches of configured regexes, a linter that uses the same configuration and shows any configured lint messages on the matches, a CI job that asserts that the matches found are only in the allowlisted files for each metric, and a website that displays the latest data, shows graphs of the metrics over time, and integrates with our ownership system to show reports for each team & the breakdown across teams. The website also has the ability to send emails and slack messages to teams involved in each migration, and when the configuration for a migration includes a prompt, can start a job for an agent to attempt to fix the problem and create a pr.