With decaying orbits, the point of reentry depends heavily on solar activity, and is very hard to predict or control.
When there are things that could survive reentry and potentially be harmful, or humans and equipment you want to recover, you would wait until you reach the right spot in your orbit, then fire your thrusters against your orbit to slow you down enough to head back towards the earth in a controlled manner, roughly where you want to be.
Could this be achieved with ion propulsion?
Is the typical amount of ion thrusters mounted on satellites sufficient to deorbit in a timely enough manner?
What about controlled decay, could you use it to simulate a constant atmospheric drag, by compensating for solar activity?
If left to decay on its own through atmospheric drag, the moment reentry happens could vary by a few hours due to solar activity.
My question is about choosing the general point of reentry (a specific region or zone), not about aiming the spacecraft on a small ground based target.