I think you are viewing trucks as just trucks. They are much more than that. These territories are in many cases the size of entire nations, so the “front lines” thing is not really what is going on. They are just bringing stuff to the front from factories or mobilization centers.
I suppose now I could advance a new concept:
Trucks are placed in controlled spaces and are used a ‘jump points’ for units boosting them +1 movement, but allowing multiple jumps. Every other space is where you place a truck, which allows the land unit continuous movement to front lines.
What i mean by this new concept is you can “chain” the trucks in a row, allowing any one land unit to move and continue moving along this chain.
Enemy player can now also bomb the chain and disrupt the logistical flow, so you must use land units to protect the trucks from bombers ( combat is done in normal manner)