Now that IS a possibility, but not user/pwd but rather hardware provisioning on the MAC address.
a) setup dongle->system and get connected. Then run ipconfig /all and document the Physical Address. . . 00-0F-ZZ-AA-CC-DD
b) logon the router and look for masquerade mac address, or use this MAC address and enter the value found above.
*many* ISPs use the mac address of your system to ensure you are their customer and reject the connection if not found. I had to do this with Timewarner and my Netgear router - - very common.
ONLY a DSL connection needs to dial-out. A Cable or Satellite connection is a constant connection via DHCP.
Well, it has to dial something to establish connectivity with the ISP. You have to dial into their PPP server. The user has to run the connection application to initiate the connection.