Delay to 2022, set up a system where multi nationals and collaborators can choose to leave, pull the army out when that process is complete.
Not difficult. And no, the 'consequences' of doing that wouldn't be anything to write home about; the Taliban, provably, had no offensive capability against the US, there would be nothing they could have done about it.
Not really, Tubey, and to be honest I think what you have proposed here is pretty much what Biden was trying to do (albeit with a different date).
For a start, the moment where a system is established for "collaborators" to leave is the moment anyone eligible does leave - you've just announced to them that they are not going to be safe after you do leave (ie: that the Taliban will be in power). Announcing that would create pretty much the same sort of progressive collapse and panic we saw in this reality once the Taliban started their advance, and lead to similar scenes - who in your version's ANA is for example going to stand and fight when they think there is a time-limited window to escape? What government minister is going to devote themselves to their country, as opposed to getting out with their ill-gotten gains?
TBF I think the only way this would ever have worked would have been for the US to bail overnight, without warning but after ensuring the ANA had the capability to fight properly (supply and maintenance included) and with the requisite support when needed from US forces. The Afghan government, collaborators and all, would have been thrown in the deep end but would have had to fight. That would though have probably resulted in a long and bloody civil war, with an uncertain outcome.