Adding Free unlimited WiFi access to customers

So you could always purchase a separate wireless router for guests, and properly configure it to have a different WAN internet IP address; this could be done with the purchase of additional static IPs from Comcast, or by foregoing the static IPs and just using dynamic addresses (you get up to 5 different dynamic IPs in that case)

Though I will mention, that doing this is technically against the Terms of Service, i believe.