Trying to use existing tools (Broken Link Checker plugin) to replace shortened URLs in a test import of my birdsite archive to WordPress. “Fix redirect” works perfectly on plaintext URLs in post content (but not titles), and doesn’t alter anything else including timestamps in drafts.
Unfortunately, t.co returns a 200 OK to its requests, instead of the 301 redirect it’s supposed to, so it’s only working on the oldest tweets that predate the shortener.