Allow more functionality for alternate email addresses in email assist

I was surprised to see that you can only change the domain when creating alternate email addresses for Email Assist. I don't really understand how this solves anyone's use case?

What I want to be able to do is use a generic email address like csm@gainsight.com, but no matter what domain I configure, I'm stuck with the email still using everything left of the @ sign of my own email address. So it shows up like "sengel@csm@gainsight.com." Even if I changed it to sengel@csm.gainsight.com, it doesn't serve my use case at all. I want the email to show as a generic email address.