No, you would have to turn all routing functions off all together and turn it into a AP. If I understand your connection (and I very well might not) correctly, it uses a web based registration from a DNS redirect. And what ever IP(and Mac address attached) it sees registering, it allocates the bandwidth to that. The system can't see the 192 IP each computer is giving, only the IP the network is giving the router. If you turn off the DHCP, all it will do is not give out private IP's. So computers won't even connect to the router.
Long story short, I think the network is designed like this to specifically limit the bandwidth to each device. I would check out this link, to try to turn the DIR-615 into a AP. It is possible each Ethernet wall port only allows 1 IP through, and if so, your out of luck I think.