Using email addresses as login ids is a bad design because makes it virtually impossible for your users to change their email addresses. Talk to people who used their office email and later changed their employer, people who want to abandon gmail for privacy or other reasons, or whose email provider simply went out of business.

I would be surprised if your app would have a "change your email/login" function implemented.

1. Generate a user account ID and password for me. 2. Email them to me. (Format them as a “magic link” if you wish) 3. Delete my email address.

Easy.