There's lots of information on using one email for multiple accounts, but how about the other way around? I'm building a service and considering allowing users to log in with any of their registered emails, using the same password for all of them. Instead of a "my account is my email" mindset, I'm going for a "my account has emails that I can use to access my account" mindset.
Aside from increasing the discoverable routes of entry for an attacker, are there any security downsides to this?