withdraw from both Saudi Arabia and Afghanistan if the Taliban and Al Qaeda agree to stop trying to conquer Afghanistan.

You should hold a conference with the Taliban and al Qaeda, separately or together, within 3 months. There you propose that they agree not to continue their efforts to conquer Afghanistan. In return the US and Allies would promptly withdraw from Saudi Arabia and Afghanistan. This would solve 2 problems: 1) Saudi Arabia would no longer be a sore issue. We can easily base in Kuwait or elsewhere. 2) The Taliban will otherwise continue the war once we leave, but if al Qaeda were on our side on this, the Taliban may agree. If the Taliban broke such an agreement, we would simply return to Saudi Arabia, but all would blame the Taliban.
We seem unaware that we are in a Vietnam-type situation. We must take some risk in order to avoid that failure again. We'd confer on other issues too.