A Loya Jirga that keeps the current Constitution in place is doomed to failure.
As long as Karzai is willing to fight to the last American, we get primary authority in that country. I have seen the ANA just sit in their FOBs all day while the ANP and ISAF do the brunt of the fighting. When the Afghans step up, they get more say.

Non-concur on Karzai supporting McChrystal, unless to give support to McChrystal's excusal of ANA non-performance on the battlefield due to "A poverty of resources."

While lip-service is given to fighting corruption, the money is still flowing into Karzai's coffers, AWK still is de-facto governor and chief drug runner in Kandahar, and the elections were so ridiculously rigged that our continued expression of Karzai being "the elected leader of Afghanistan" is a joke in Afghanistan and out.

If in fact he calls a Loya Jirga (which he really has to) the results of that Jirga will be the deciding factor. I believe he will buy off the attendees and maintain the Status quo. While hiding behind the fig leaf of using Afghan traditions.

We will see. I am not (obviously) optimistic.