Actually I had tried to contact D-Link first, but made the mistake of using the support page on their website. My message there was ignored, and the phone number they give is for warranty or support contract issues.
After I posted here I got a phone number for pre-sales support (FYI: 1-800-326-1688, option 1). The short answer is no, the DSR family can't do that. I could do something similar with the DFL family, but that's beyond the budget.