As the Molot pointed out, my question is crap.. so, ignore?
Current plan is to simply drop-in the existing authentication scheme and associate successful logins with the new accounts. Somehow..
Original cruft for posterity/horror:
I've hit a logistical road-block migrating a site from LAMP stack into Drupal.. none of our users have email addresses listed.
We previously used reddit OAuth, so they just hit Login but only their Username was ever saved.. ergo we have no idea what their email address is!
How can I import hundreds of users without MAKING them re-sign-up.. possibly breaking a trust with the community?
My idea is to simply spoof phony email addresses, and somehow hope that it works when they try and login again using their OpenID creds.. but I'm thinking its never going to work.
We have the https://www.drupal.org/project/social_login system in place to handle multiple types of site login providers, however the origin site only used reddit. perhaps we should simply lock it down to a single source again, and slowly open it up again after relaunch..
Alternately, perhaps I should simply modify the social_login system itself to detect an existing user from the original OpenID provider and link the accounts then and there, perhaps asking for an email address at that time.. Dunno.
I don't think this issue is the same: https://www.drupal.org/node/1955820 as I don't have an email address to match.
The module seems to use:
social_login_core_get_user_for_user_token($user_token); to restore the login for existing users, except we won't have associated that users token yet, as they won't have ever logged into the new site.. I'm sure there is security issues surrounding things like this that would break my desire to simply grab all the user-tokens for our existing users?
IDEAS INCREDIBLY WELCOME!
I'm leaning towards the garbage approach illustrated here: Ignore "invalid" or incorrectly formatted Emails addresses (on Signup/User Import)