Config question: substitute another attribute for username

I have a wireless system that can talk to RADIUS to control access for the wireless stations. The AP is a NAS and the stations can be programmed with a username and password. The idea is you reply with VSA's that set up QoS policies for the clients. This is all working fine and dandy. What I'd like to do is actually ignore the username and password they're sedning and instead match a vendor specific attribute called DAN-CPE-MAC-ADDRESS. Alternately, they all come with a default username set in them. Will there be any harm if I make multiple users with the same name? "cpe1" DAN-CPE-MAC-ADDRESS := "0a:0b:0c:0d:0e:0f" "cpe1" DAN-CPE-MAC-ADDRESS := "01:02:03:04:05:06" etc etc.