All of that militates for appointing someone to the Pentagon whom the building trusts.

Yes, but if the only reason for keeping Gates is this political one, there have to be others that would meet that criteria. You mention two of the most obvious, and their probable reasons for declining, but certainly there are more. It is also critical that the person chosen have the trust of others. Given the DOD shenanegans not just over things in the past like Abu G. but the current show trials at Gitmo (who really needs decent interpreters, anyway?), DOD must have a new head to have any credibility OUTSIDE its own five walls.

How about getting Webb and Zinni and a couple of other folks who are well respected by the officer corps to suggest a couple of names to Obama? If Obama says “Give me five names, and I’ll pick one of them,” it’s a gamble on his part but also a sign of his willingness to pick someone with obvious credentials and support both inside and outside the military.