The TF: Animated Optimus Prime mystery

So, as most of you know, in Transformers: Animated, Optimus Prime will have a Fire Truck as his Vehicle Mode, but only the truck's cab will become his Robot Mode.
the mystery is, what will be the use, if any, of the back section of the Fire Truck? my guesses are either:
A) a mobile command center,
B) armor for a "Super Mode", or
C) a stationary projectile weapon(a laser cannon).
anybody else have any ideas?
the mystery is, what will be the use, if any, of the back section of the Fire Truck? my guesses are either:
A) a mobile command center,
B) armor for a "Super Mode", or
C) a stationary projectile weapon(a laser cannon).
anybody else have any ideas?