Why was the possibility of just capturing Abu Ahmed never discussed? As he was the only contact between Osama and the rest of the world, removing him would force Osama to take action and reveal himself.
If Abu Ahmed was captured, Osama would run, rather than stay in a fixed location. If Osama clears out of there, he would have pre-prepared escape routes and would likely be aided by Pakistani military/intelligence services. There's a good chance he would elude observation and capture, and the hunt begins again. Better to let him stay in place so they can plan and launch an attack at a fixed target instead of playing the hunting game again.