I don't think this addresses the issue. First, I think multiple representative agents have to be carefully defined to generate an equilibrium solution -- which

I don't think this addresses the issue. First, I think multiple representative agents have to be carefully defined to generate an equilibrium solution -- which implies some strong limitation on the space of possible agents. Second, and more important, you have not described the "Buyer beware" message you claim is implicit here. What limitation does the requirement for representative agents impose on the behavior or range of applicability of these models? Unless you can get specific about that we have to fall back on our dark suspicions.