To some extent they must take currency risk into account, so what what would their base currency be, yuan? In which case they will always give China a AAA rating?
The US agencies similarly could justify always giving the US a AAA rating.
Ratings based on gold would be interesting, Australia might still get a AAA rating as the world's 2nd largest producer but would need to pay something like a 10% bond yield to keep up with gold's year on year appreciation (actually $A depreciation vs gold)
