I have around 100 domains and only "use" about 10 of them. I'd be interested in being able to upload a "portfolio" listing all my domains that others could browse. If another user wants one of my domains, a message would be sent to me. I could then browse their "portfolio" and see if I wanted one of their domains. If so, a 1-to-1 trade would be proposed which both parties would then have to agree to. At that point, we would each transfer the domains to the other party (without some type of escrow, you'd be on the honor system and have to trust the other party, but some type of "reputation" or "karma" could maybe be implemented for that?).