Given how we are yet to see John Giant or any of the giant VAs do anything, I think there is a very high chance they will have a role in Elbaf. It is the land of the giants after all.
My guess is, there is a marine base on or near elbaf. This is where the giant squad is stationed and John Giant is likely the commander of this base.
Regarding what John's specific role is, I believe he is supposed to serve as a foil to Saul. Saul was a giant who joined the marine, just like John Giant. However while Saul ultimately defected in order to follow his own code, John Giant didn't. I think ultimately, John Giant will be Saul's main fight, if not in elbaf, in the final war.
My guess is, there is a marine base on or near elbaf. This is where the giant squad is stationed and John Giant is likely the commander of this base.
Regarding what John's specific role is, I believe he is supposed to serve as a foil to Saul. Saul was a giant who joined the marine, just like John Giant. However while Saul ultimately defected in order to follow his own code, John Giant didn't. I think ultimately, John Giant will be Saul's main fight, if not in elbaf, in the final war.
