when i played the original Final Fantasy XII (not International with the Zodiac Job System) i remembered that Guests could not be controlled or have their Gambits accessed. this went along side with what Balthier said when Amalia first joined
Think of her as a Guest. our "Guest" will do as she pleases won't be taking orders from anyone and will leave when she pleases it
And i do recall not being able to issue commands in battle to guests because i never came across their command window when issuing orders.
So this got me thinking, aside from having the Zodiac Job System are there any other functional differences between the original Final Fantasy XII and Final Fantasy XII: The Zodiac Age?