Civ attributes should change with time. For example, a trigger like a Democratic Revolution should change the leader and civ's official name.. Perhaps even diplomatic stance with other countries (Different government types would start of being friendly with other civs of the same government type by default.. even if they were at war just a few turns before)..

The control over this aspect should be in the civ's rules.txt

Example from c:\Civ3\Russians\rules.txt

[TRIGGER]
GovtType=Communism
ChangeLeader=1
Leader=Vladimir Lenin
ChangeOfficialName=1
OfficialName=the Union of Soviet Socialist Republics
ChangeCountryName=1
CountryName=USSR
ChangeAdjective=1
Adjective=Soviets
St. Petersburg=Leningrad
Kharsk=Stalingrad
CreateUnit=(24,48),Partisan
Industry=x+4
Message=Bolsheviks caputure power in Russia. Vladmir Lenin proclaims himself General Secretary of the Union of Soviet Socialist Republics.
If
GovtType=Communism
then
Message=Dawn of new relations with USSR. Soviets and [adjective] declare themselves as brothers..

Something like that