Then set up a script that migrates your subscription list to the new account

No need for that, you can export your subscriptions and settings on your profile page.

You can use this script with a browser addon like Tampermonkey to get around the sign-in requirement:

// ==UserScript==
// @name         reddit - unblock (create cookie and reload)
// @namespace    Violentmonkey Scripts
// @match        *://*.reddit.com/*
// @grant        none
// @version      2024-01-08
// @noframes
// @license      MIT License
// @description  for "Blocked" "whoa there, pardner!" cowboy bs
// ==/UserScript==
/* thanks: https://www.reddit.com/r/mullvadvpn/comments/18jbxb2 */
if (document.title === "Blocked") {
  document.cookie="reddit_session=;Domain=.reddit.com;Path=/;Expires=;Secure=true;SameSite=None";
  window.location.reload();
}