OK - some people will always want to do drugs and frankly currant drugs laws have been a total failure. Anything that stops nasty people getting drug money is a good thing but since our rulers and foolers like to be all holier than thou and 'hard on crime and the causes of crime' we are cursed to have street crime and black money going to criminals and terrorists. Just f' great. Thanks.
Gassing, poisoning and spraying chemicals over vast swathes of Afghanistan - a good idea? No - it wasn't a good idea when Mussolini did it in Ethiopia, it didn't help when the Americans did it in Vietnam; public opinion would go ape-**** and the populations thus affected would have a greater reason to want to kick out the occupiers and support the Very Nasty People.
Now it seems to me there are some fairly / relatively wealthy people in Afghanistan and they live in towns and they want a democracy and they want a peaceful place so they can encourage investment, cream as much off as they can and then go about making money and being decadent and such. And then there are these people out in the countryside and some of them just want to be left alone, some of them hate the occupying forces and some of them wish that the taliban would chill out and just let people get along. And it seems they don't really want outside help that much because they know one day it'll move out and then it'll be a case of 'You fraternised with the enemy you collaborator so now we take revenge.' Which isn't nice.
And of course there is the issue of this Allbranistan (for there will be another) currently being a focus for everyone that doesn't like damn western christian imperialists.
You can tell that our great leaders are slowly getting utterly fed up with these wars upsetting the opinion polls back home and oh how they wish it would go away. So they'll want an out soon. Even if there is a 'surge' it'll be to set the scene so they can get out and say 'Now it is up to you Mr. Middle class of Thisstan 'ere.' And then they'll be off out saying 'Job well done - exit with honour, heroes all.'
In summary - look after the towns, set up as best can oases of security - leave.
In about 2 years I reckon.