Well the caveat would be that I would prefer ratings from people who could at least rate say half the nations in one or more particular ages. This is to show a breadth of experience that enables one to reflect more adequately upon their experiences, rather than only being familiar with 3 nations, and rating them only relative to eachother (then it becomes another shallow "rankings" exercise).
As far the MP rating, I would definately prefer players who had at least completed 3-4 full games. Obviously it is best if some of those games they survived to the end, and even better if they've even won 1 or 2 of them.
There would obviously need to be some sort of oversight, using the pseudo-Olympic model, anyone whose scores deviate significantly across the board from everyone else, would likely be disregarded. Not to say that people can't disagree, but if someone seems to "disagree" with everyone else on everything, they are likely insane or just like to cause trouble.
I suppose Endo, you make a fairly good case for taking the numbers away from the submitters, to give them a clearer sense of what they are stating. Ultimately, the more contributors we get, the less accurate their rating needs to be in order to get an average that IS accurate. Though I think if I do so, I will use the designations of "Sad, Weak, Capable, Strong, Glorious".
I don't know, maybe it's my sense of creativity that just prefers numbers for such things, words are so arbitrary, numbers always say what they mean.