The full question: is it possible to remake a documentary as a documentary? We know, thanks to Werner Herzog and others, that you can redo a documentary's story as a dramatic feature. But let's imagine instead that the premise behind your favorite classic non-fiction film is lifted and re-applied to a new non-fiction work with the same title. 'Hoop Dreams' following a new set of high school basketballers. 'Salesman' documenting today's very different breed of door-to-door merchants (of bibles again or something else). 'The Thin Blue Line' investigating another murder. 'Primary' observing a 2012 Democratic (or Republican) primary election. 'Nanook of the North' presenting the life of the Inuit today.
Actually, 'Nanook' could simply be redone shot for shot. The original isn't exactly a document of an Eskimo of the time so much as how the people used to be, prior to European influence. But then, the remake would be even less qualifiable as documentary than Robert Flaherty's 1922 version. It is an interesting film to bring up, though, because it was already remade in a sense. In two senses, as a matter of fact. The classic we know of now was in a way a redo of an earlier film Flaherty was working on but accidentally destroyed. After 'Nanook' became a huge international hit, Paramount Pictures pretty much asked him to remake the same film (literally they requested "another 'Nanook'"), only in Samoa. The result, 'Moana,' doesn't look or feel the same, however. This is partly why it bombed.