Email aliases can confound group Owners, who often don't even realize such a feature exists. For example, it's very disconcerting to attempt to invite or direct add an alias address and have the system tell you that address is already a member.
"??? I don't see it in the Member List..."
Even if you do already know about aliases, this leaves you with the frustrating task of painstakingly opening every member record one by one to find out which account is using the alias.
To that end, it might be handy if all aliases were listed right there in the Member List, perhaps indented below the subscribed address and in a different color (or bearing a new status badge or something along those lines...haven't thought that completely through). Failing that, if you attempt to invite or direct add an aliased address, the error message could say something more helpful, along the lines of "already a member (as an alias of xx@ yy.com)."
A final thing I would like to open for consideration is the ability of Owners of Premium groups to edit a subscriber's email aliases (as they already can for the primary address).
Thanks for your consideration,