This is written from a "We are there, dammit" viewpoint; has little or nothing to do with an independent strategy vs AQ (Astan & AQ are better considered as separate problems); and is suggested more to allow time to coldly consider whether an acceptable (note "acceptable") political effort can be mounted in a more limited geographical region.

This pertains to Entropy's nugget (post #22):

I don't think that's necessarily the case, at least the writing off Afghanistan part. One could shift, for example, from a strategy designed to defeat the Taliban to a strategy designed to prevent the Taliban from winning. We'd be ceding most of the Pashtun areas, but we could certainly prevent Taliban control over the non-Pashtun areas, which is a significant part of the country. In other words, it's not all or nothing.
but is more particularly based on his maps to be found here.

A demographic line approach was suggested for Vietnam (Krepinevich, The Army & Vietnam, pp.266-268). I floated a form of this using Highway 1 as a rough demographic line in another context - this post and this post (maps), forcing through a Peace Enforcement strategy (e.g., Joint Pub 3-07.3, Joint Tactics, Techniques, and Procedures for Peace Operations, Chap III, as updated by more recent operations); and, in effect, offering the Taliban a limited truce if they stay south of the Tripfire Line.

This Peace Enforcement strategy would be of little comfort to those who want either a minmum force increase, none or an immediate force drawdown. The 40K to 80K increase would be, if nothing else, a good PSYOPs move (by not indicating a current intent to withdraw - as we did with Vietnamization); that increase would be incremental and take a long-time (and could be halted at any time).

This strategy does not in any way change my opinion that the prospects for an acceptable future political effort are lousy (a classy legal term ); but, if an acceptable political effort cannot be mounted in the "Northern Alliance" region (above the Hwy 1 line), it cannot be mounted.