That's pretty fantastic, but the citizen wouldn't be able to pass through the shielding just because they're in a Combine affiliated vehicle, because the citizen himself is not affiliated with the Combines, so much like Gordon, he would just collide with the shield, and since he is in a vehicle that is affiliated with the Combines, his entire body would get crushed, broken, and torn to pieces between the vehicle, and the shield gate
Or so i would imgine
that was one of the ideas that i had, he'd try to drive through but get smushed (in a less gruesome way) in the way you described
then i was going to have him hop on top of the apc and just try to hurdle over the shield
except the smush is a bit tricky to represent in animation
plus i really have no idea how those shields work, i had another forcefield-related idea in episode 1