Logging in with name (not email)

I have a site (Plone 5) with login set to 'email'.

I need ONE user to be able to log in with just username.
Is this possible (now, if I create a new user, I can only log in with email, not username)

add the user at Zope level.

One caveat I've experienced so far: This will land oneself in hot water if plone.rest or plone.restapi is used by that user as it cannot figure out the user being from a different acl_users.

Works great for this use case... thanks