IF the US were to strike as far as Quetta, it would mean one of two things, and BOTH make actual drone targeting and tactical issues pretty much irrelevant:
1. Pakistan has agreed to such strikes. In that case, it means Pakistan has given up the "good taliban" (betrayed them?) and in that case, you dont really need drones, low paid pakistani police officers could do the job (and the surviving members of the "shura" would escape to the badlands or back into afghanistan, not stay in quetta). Individual terrorists can certainly hide in big cities, but then they are much more hidden to drones than they are to the local police.
My point is, if the Pakistani state ever decides to betray their friends, then its not a drone issue in big cities like Quetta (this is NOT the case in the tribal areas..there the pakistani state may have even less reach than the drones, so drones may be needed even if Pakistan is one hundred percent cooperative, as is maybe the case in South Waziristan?)
2. Pakistan has NOT agreed and the US has decided it doesnt care. In that case, the US has many more direct ways of making Pakistan change their mind and those would probably be much more important than hunting for a needle in haystack in a country where you dont have too much good intelligence. In other words, why look for an invisible shura in a "hostile" country when you can look for the very visible prime minister and have HIM change his mind about cooperation....
Just my amateur thoughts