I would be interested in some kind of "show of hands".
If we were to band together we might be able to get some kind of special treatment... I think professional associations get a $250pa reduction in fees on this card, for example. I would imagine you would need to collect names from interested people, and nominate one person to handle the negotiations with Amex. Given the strong opinions of many here on AFF, whoever was in charge of negotiating with Amex might find it difficult to achieve a consensus of interested card-holders, which would weaken the negotiating position.
Re: comparison with Singapore, US etc. This is tricky as each country has different sign-up bonuses, reward partners and complimentary features (eg I think only Aus and Canada get Marco Polo gold, and I know the sign-up points are much bigger here than in the US). On the other hand the price difference is very significant, and it would be interesting to see if Amex can be bullied... I mean persuaded to exercise some discretion for some of their more savvy clientele.
Another thought: if Amex ever got hold of the list of names, they might use it to select people for "financial audit". Could be difficult.