Ability to add @username on Builds emails

If I want to add some members to Builds emails field (https://<host>/<namespace>/<project>/services/builds_email/edit), I have to type their emails.
But emails bring a bit problems here:

1. What if some emails will be changed? Then I will have to go to the page again and replace the incorrect email by new one.
2. If I want to set many users at once, I have to open each user page, see public email, copy it, return to the Build emails page / tab and paste copied email there.

So, my proposal is to add an ability to add @username instead of email or as an addition to emails.