The answer would largely depend on how large the focus area is or how fast the signal quality degrades the further from the epicenter of the focal point that the receiver is.
Maybe the system could apply road map info to fast-moving cell phones which it can assume are in traffic. And this could help it predict possible future locations of your device.
For much of the day the majority of devices in a given "cell" will be semi-immobile at a desk or slowly moving when someone's walking.
I think an on-board "repeater" would be the best solution. Of course, a high-powered directional antenna would translate to less hopping between towers but also increased costs to the carriers. Something like Google's Loon project might have more coverage and work well with aircraft.
Maybe the system could apply road map info to fast-moving cell phones which it can assume are in traffic. And this could help it predict possible future locations of your device.
For much of the day the majority of devices in a given "cell" will be semi-immobile at a desk or slowly moving when someone's walking.