Just on the basis of government experience, such an appointment seems plausible: Richardson — at least on paper—had the most impressive resume (sitting governor, former congressman, former UN ambassador, and former cabinet secretary) of all the Democrats who ran for their party's 2008 presidential nomination.
Likely of more interest to VDARE readers is a brief conversation with Richardson reported on page 3 of a Center for Immigration Studies backgrounder, Immigration and Usurpation: Elites, Power, and the People’s Will, by Fredo Arias-King:
Bill Richardson, who had served in Clinton’s cabinet and later became governor of New Mexico, kindly stopped to speak to our delegation at the  Democratic National Convention in Los Angeles. He commented favorably to us: ”What do Hispanics want? Fully funded government programs!”Put another way, Hispanics, as a class, are natural Democrats.
To complete the picture, then, what don't Hispanics want? For most of them, enforcement of U.S. immigration laws is apparently high on their anti-hit list.