I don't know how different it is on mac but i'm guessing its the samething. Anyway go into data\world\maps\campaign\imperial_campaign == descr_strat and change this.
Code:
campaign imperial_campaign
playable
romans_julii
romans_brutii
romans_scipii
end
unlockable
egypt
seleucid
carthage
parthia
gauls
germans
britons
greek_cities
end
nonplayable
romans_senate
macedon
pontus
armenia
dacia
numidia
scythia
spain
thrace
slave
end
to
Code:
campaign imperial_campaign
playable
romans_julii
romans_brutii
romans_scipii
egypt
seleucid
carthage
parthia
gauls
germans
britons
greek_cities
macedon
pontus
armenia
dacia
numidia
scythia
spain
thrace
end
unlockable
end
nonplayable
romans_senate
slave
end
Hope this helps.
Oh and i have left the Roman Senate and slaves locked in the above example. I have never played with them unlocked but i hear the Senate can course CTD's when opening the senate info page, ie. Delopmacy, senate missions etc etc.