Use your imagination!
Imagine Madeline Halfbright debating with Rumsfeld.
And if they don't accept the invite, well Bush can always say he extended the invitation and welcomed their expertise.
This isn't the sort of thing one goes into and spouts silly partisan talking points. He's cast down the gauntlet. Frankly I see it as a bit of genius.
You nailed it.
Bush will come accross as being open. However, he and his team will kick the opposistion's a$$es.
Picture this we have President Bush, Rice, Cheney, Rumsfeld, Shultz, Baker, and Kissinger. and they have Madeline Not-so-Bright.