First of all, you cannot get the registrars to cooperate; most seem to hate each other, or at least not trust each other, and secondly, you get into a potential situation whereby the registrars are tempted to park their own domains, an allegation that goes to GoDaddy as well.

As an example, we registered a set of domains through GoDaddy, and now are getting repeated offers for a related one which is one of the many, many 'Domains by Proxy' registrations at GoDaddy. As has already been pointed out, GoDaddy could be front-running domain registrations and no one would be any wiser. The vast scale of the company means they can see trends and preferences on a macro scale before you, the lone domainer, can see it on the micro scale.

What will work is a web site that simplifies the process for someone who wants a specific domain. What exists now is basically a combination of flea market, classified ad listing and carnival barker style auction.