The main goal in any war is to compel the enemy to do your will. You don't necessarily have to annihilate his fighting forces to do that- although many times that's what ends up happening.
The Taliban existed in Afghanistan long before we invaded, and if they hadn't allowed AQ to use their country as a base to attack us, the TB would probably be in power there today. If the TB will completely break with AQ, and will adopt a political position that is acceptable to our values, then I'm OK with some of them coming back into the government. The two conditions that must be met first are that a) we must negotiate from a position of relative strength, and b) we must kill the insurgent leaders who will not reconcile.
But would the TB "sell out" their extremist brothers for peace? You're talking about people who think to die for Allah is glorious, so how do we leverage them to break with AQ?
I don't think we can trust many TB to do that. Remember this is a culture who accept duplicity in dealing with each other, to think nothing of us kaffirs.
I think there are some TB we can work with, but the majority could use a JDAM or two in their lives. Or AGM-114's. Or 5.56. Or 7.62. Or.....