See - now why does it have to be the extreme? Why is it that if one person is suggested, your response is that I think there's no Dem who can serve on National Security issues? You're asking a guy who joined State because of Madeleine Albright and then quit because he felt let down by Colin Powell (of all people) if he thinks there are no Dems that can handle National Security issues. Ridiculous.
David Brooks is not asking for all of them, but he's asking for a couple, and there's nothing wrong with that.
The Gates one is an easy one - ask him if he supports and can accomplish a calculated troop withdrawl and if he agrees, let him do it. When he's done, replace him. It's actually, the most efficient way to get the job done and would probably save 6 months time.