MIC, Military/Industrial Complex essentially refers to the Barracks Buildings, the other I think you are looking at govt types I, II, III, IV.
Govt type will affect what units you can raise in a city, types I and II mean higher end factional units, types III and IV will allow more regional or local types.
Be aware with the Romans that until the Marian reforms you can only recruit "Roman" units in Italy.

Intanetusa have you tried Konny's allied legions mod that gives you Ligurians, Bruttians, Hoplites etc through your Faction MIC's, makes raising realistic armies easier and provides some nice variety.