You make great points...and I think that President Bush had to think of those ramifications if he went along with the invesigation...
BUT, I am sure he weighed the chances of your scenario against the absolute coup d'etat that REPUBLICANS might have attempted if he didn't...and capitulated.
I think he also knows that laws would have to be passed to make the process any different than it is now...and if this investigation shows (as he believes) that the deal SHOULD have been allowed anyway...then maybe he thinks the legislation may be less drastic...
BTW...this is Busbot sleuth talking here...LOL
Has Sean even mentioned that President Bush stopped in Afghanistan today???