I think it's much easier for the REVIEWER to review on simple terms. It's up to the maker of the chart to make a good chart out of that.
"Very weak, weak, average, good, very good" would be better than the weak/average I used above. If I make a new thread where people can post their opinions of nations with this five-point scale, I think it could really catch on. I'll wait until you decide how, exactly, you would do the scoring.
Here's what I suggest. Just exploit the fact that 0 out of 10 is NEVER given. Even the worst games or movies will get 30 out of 100 or 2.5 out of ten or half a star out of 5. Five scores is still enough to calculate averages - 3 votes for strong and two for very strong gives nice 8.8 result.
Code:
Very weak | 2
Weak | 4
Average | 6
Strong | 8
Very strong| 10
This way, the lowest score any nation is likely to get in any single score would be slightly under 4. Ease of Use of 2.7 or whatever for Early Mictlan would be suitably bad. If it actually had a score of 0.8 or something, it would turn people off instead of just warning them. "Worse than Descent to the Undermountain? I'm not going to touch that!" etc.
Also, if we get a good discussion rolling AND we get the short summaries about the nation, it'll be a great addition to the StrategyWiki. We'll take the averages out of the chart, and add the comments about the various stages of game, and we have a short strategy guide and review.