Hello @LotusJeff
Did you have a look at these settings, as I think they will get you some part of the way there:
Configure these settings in /admin/settings/
| Setting | Suggested Value | Effect |
|---|---|---|
purge_unactivated_users_grace_period_days |
1 | Deletes unactivated accounts in 1 day instead of 14. It is’t instant like asked in #2, but it’s the same effect with a smaller delay. |
blocked_email_domains |
Add known spam TLDs/domains manually | Blocks registration from known offenders |
For anything fully automated like you ask, I think a plugin would need to be built (or none exists afaik), or you can take a look at the new workflow feature. I don’t know if what you want is possible yet, but it’s updating almost daily so who knows 
For the plugin route, there is an event you could hook in DiscourseEvent.on(:email_bounce)
Also worth looking at Configure VERP to handle bouncing e-mails maybe