I am playing a Pergamon-led Hellenic league and for variety's sake I have decided to Balkanize Italia. I have liberated every province except Asculum (I need one to base my garrison in), but regrettably I had to declare war on all my new "allies" and defeat them to vassalize them. It would make a great deal more sense if I had an option to liberate them as a vassal to start with -- Rome did this many times over the course of her rise, and the Hellenistic states did as well.
Is this possible within the game's constraints?