I like 4,5 and 6.
I think 3 is too restrictive - I imagine there are plenty of important facts that there is only really one source for. Any other source for that information would be getting it from that one source anyway, so citing 2 sources would be meaningless.
I think 1 and 2 would encourage systematic bias. Requiring people to appear in encyclopedias or Who's Who would cause a pro-western bias, I expect. Requiring people to appear in newspapers causes a bias against fields that don't get much news coverage (to be honest, I can't think of an example of such a field at the moment, but I think that's just lack of imagination on my part).