Some Brief Questions (From a Noob)

[Zrk2]

Will the "Camillian Military Era" building thing change as soon as this happens, or do I have to destroy the barracks first?

[vollorix]

The switch from Camilian to Polybian era does not require destroying your barracks, just upgrading them, sometimes. It´s the "Marian Reforms" when you need to raise down your old barracks and build new ones ( a script will keep damaging the Polybian barracks every turn, btw. ). The "March of Time" reforms, if you want to call them so, do not actually affect Roman faction, but do change some bodyguard types for factions like Pontos, Baktria etc. And it occures simply through upgrading an Italic settlement to a huge city ( Capua, Arretium, Ariminium, or Arpi ).
Edit: Oh, and MoT also enables the "Greek Reformes", when Macs get their Phalangitai Reforms, inabling them to train well armoured and tough line troops, available everywhere they got Type 1or 2 gouvernment buildings, and KH should become their own factional Phalangitai too.

When playing Romans, you´d need all those lvl 1 and 2 government types to be able to build your factional barracks later, when "Marian Reforms" have occured. And, as you already noticed, they allow you to build more advanced structures in those settlement, due to the higher speading of Romand culture, so to say.
Building Type 4 you actually establish a client kiindgom, and do benefit from the largest variety of local troops, along with experience bonus given to them through that building ( +1 ). It all depends whether you are trying to play more "historically", roleplaying your faction/family members, or simply using the best suited gouvernment type, saving time to advance faster, for example, or all together.

[Zrk2]

Oh, okay. That clarifies it. I thought the one I got meant I had entered the Polybian reforms, but it only reformed some other factions. That would make sense as, on further investigation I have not fulfilled the requirements for the Polybian reforms yet.

Thanks for the help.

[Zrk2]

Double post, I know, but I just wanted to tell you that the Polybian Reforms just triggered and I am currently upgrading my MICs to take advantage of them.