The kind of user who could modify chrome to subvert the will of administrators is the kind of user who could figure out a way around the root restrictions in th

The kind of user who could modify chrome to subvert the will of administrators is the kind of user who could figure out a way around the root restrictions in the first place, most likely. If it is a virus/exploit issue that you are worried about, my bet is that an auto-updating chrome is better protected from these than a root-restricted but out-of-date browser.