Crucially, also, no one wants an army that is actually capable of taking on and defeating the next government of Afghanistan – the Taleban.
I disagree. The army is largely non-Pashtun. 70% of the officers corps is Tajik. In an ideal world the Afghan army would
be able to suppress the Pashtun (/Taliban) - do the job the ISAF forces are doing. Unfortunately they do not have the skills, equipment, infrastructure, experience or financial muscle to do 5% of that job.
We're now, gradually, coming to a realisation, finally, that the obstacle to peace in Afghanistan is a particular ethnic group rather than an ideology, and that the problem lies with Afghanistan itself.
In this fourth step, attempts will be made to prevail upon the Taleban to adopt a more "moderate" face, ridding itself of its obvious "hard liners", who must be either sidelined, retired or murdered. The services of the CIA and its armed UAVs, or the special forces, may be offered to help remove any obstacles to "peace".
This is hard due to the tribal nature of the Taliban as Pashtun. They are not moderate by who they are, and little will change that except genocide or 100 years of development and demographic change.
The so-called "moderate Taliban" are the Pashtun tribes currently excluded from the Ghilzai Taliban hierarchy who would have something to gain if they switched sides. You are not talking about the real Taliban at all but a population group that has been co-opted into its power structure on the basis of ethnicity and convenience.
What I think you are trying to say is that through bribery and the eventual arming of non-Ghilzai affiliated Pashtun (real Taliban) like the Durrani the Pashtuns can be made to fight each other and in that way marginalise the Taliban's influence to the less important mountainous regions where its constituent tribes are strongest.
I remain to be convinced ethnic ties between Pashtuns are so weak that money can buy this cooperation in perpetuity. It is more likely to back-fire, the non-Pashtun cotton-thread alliance with the Tajiks and Uzbeks won't hold, the aggressive mountainous tribe will return to power to establish Pashtun dominance on the basis of shared ethnicity.
Beefing up "moderate" Pashtuns, may foster Pashtuni nationalism where there was none, and result in an extremist Islamic state on the lines of Saudi Arabia but with an expansionist nationalist agenda that has designs on Pakistan (and a willing ally in India).
There would be better ways of neutralising the threat such as creating a Pashtunistan before the damaging nationalist wave, which is being caused by our attacking this specific ethnic group, hits... although it may be too late.