Cleaning up the #AzureAD and Microsoft account overlap

My domain on m365 is a vanity domain, it is not a business, and never will be. I'm its only user and that's highly unlikely to change. I have one mailbox configured, and it's set up as a catch-all for the domain.

Every service I sign up for I do with service-name@domain - but I couldn't do this with Microsoft. I didn't even want to use the same value before the @ as is the name of my domain's one user, but the whole domain was blacklisted. The current solution is far too heavy-handed. 

I ended up logging a Microsoft case, and asked the following:

1. If I had changed my Microsoft account address to microsoft@domain before adding the domain to m365, would it have worked as I want it to?
   • Answer: Yes
2. If the answer to my previous question is yes - how long after deleting my m365 tenant would I have to wait before I could set the address on my Microsoft account, then bring my domain back on to m365? Because as incredibly dumb a solution as that sounds, I am genuinely considering that course of action.
   • Answer: You can just delete the domain from the tenant - you don't have to delete the whole tenant. Also the answer depends on how many users, how many groups, and various other factors tied to the number of references to the domain.

In my case I had another mail provider (Google) that I was able to point the domain at for a short time, so that was easy. It took me only a few hours to redirect my mail to Google, remove the domain from m365, change my personal Microsoft account address, add the domain back to m365, and direct my mail back to m365 (though I think I was somewhat of a best-case scenario for those timeframes).

• I was not alerted that an address on my domain was already in use for a personal Microsoft account when re-adding the domain
• I have not been prompted to change the address on my personal Microsoft account
• Because the usernames do not clash (microsoft@domain and user@domain) I do not get the "which account do you want to use?" prompt.

Basically this now works exactly the way I wanted it to... it just should not have been nearly this complicated to reach this point.