Well, in the meantime I would give Syracuse somewhat better defences from the start, after all it was like constantinople in the middle ages: a very, very hard nut to crack. The romans took it only because a gate was left open as the defences were still pretty much intact even after 4 years.

BTW, if you can make an unique retinue tied to a city it would be cool to get Archimedes with an academy or something like that...