Risk vs reward, you have complete control over it.
I agree, but I do think the current system does not resemble this completely.
Putting the trucks in a very forward position can be very advantageous but gives a high risk of them being destroyed. In this case the vulnerability of the trucks is adequate. This is good.
However, the trucks remain exactly as vulnerable (HP wise) when they are set up far behind the front lines on purpose. Especially to artillery in team games. IMO, this is not good. Med and Mech truck can die to as few as two arty barrages and repairing them is extremely dangerous.
Therefore I would propose to at least get rid of the repairing penalties for Sturmpioneers when repairing trucks, so the 300MP squad doesn't instantly die to one artillery shell of the next volley.
Secondly I would propose to add a percentage of HP to the truck (to a max of regular base buildings) the closer it is to the main base area. This way choosing low risk actually means lower vulnerability.