FYI, there is a similar Feature Request (proposing an option to hide the email address), in which @tgreer had suggested implementing an account “nickname” as an alias for the email.
However, I think that you may be suggesting something different. FYI, the email address is required to deliver notices about failed login attempts and successful logins from new devices, as well as reminders about subscription renewal; in addition a verified email account is required to enable the Bitwarden Send feature.