I understand you're saying that when soaking full auto damage passengers get the armor stacked, and when ramming/rammed they do not.
what about motorcycles? do we houserule them out or do we leave them under general rule?
Characters resist ramming damage with half their Impact armor (round up).
That's all it says about ramming. So no, imo, you shouldn't add vehicle armor there. (You can get the Passenger Protection vehicle mod for extra protection, though.)
And when being otherwise attacked while in a vehicle:
... the passengers are always considered to be under Good Cover (though the Blind Fire modifier may apply to the attacker as the situation dictates.) Passengers attempting to defend an attack inside a vehicle suffer a -2 dice pool modifier to their dodge, since they are somewhat limited in movement. Additionally, the passengers gain protection from the vehicle’s chassis, adding the Armor of the vehicle to any personal armor the characters are wearing.
Plus they'll usually get +3 Moving Vehicle and/or other things, as GM decides.
Bikes... Maybe only Partial Cover instead of Good Cover, that's half the defense bonus (and then negated by the -2 to dodge). Maybe could do half armor too?
Then again, there's really no RAW for this.
*shrug* Whatever you want man, I think the GM's got the right to run his game however he pleases and I'm all for houserules as long as it makes sense and they aren't introduced/changed mid-game.
Edit/addendum:
(So, so close to finishing the char... and then I notice I forgot contacts!

)
I'm sure I asked already, but I'm tired and might be confused with one of the two (now dead) games I joined last month. Just to be clear : We don't get any free contacts?