Hartmann,
I think you should slow down a bit with adding the new nations and consider the options...
I played around with the odd left over nations yesterday and the results were disheartening:
1) Entirely new nations can not be added.
2) Of the strange leftover nations only KAL and HEI are fully functional. ITA and MER do not get diplomatic interaction even if you add them to the matrix. PIR, NAT, REB, MIN and MUS are in fact used by the game.
3) AFAIK, you can only set the tech group for nations that rebel. I have found no way to change the tech group in the .inc or .eug files. So HEI and KAL should be used for nations in the latin (Western European) sphere or nations elsewhere that may become independent during the game.
4) Default leader values may not be changed. I've not even managed to change their names, although the necessary file appears to exist in two places (DB/RandomLeaders.csv and DB/leaders/RandomLeaders.csv).
5) I've not managed to change the set of unit sprites for nations. That connection appears to exist in the code.
This gives us quite little room to maneuver. We must judge which nations that we feel are most important to add, and then use KAL and HEI for European nations (since they have the correct unit graphics). HEI could be a German state unless we can change the leader names. KAL will have the wrong leader names no matter what (unless we assign it to Finland

.
I suggest (i.e. would like to see):
KAL - Novgorod
HEI - Greece/Constantinople
These may only exist if they rebel, so the tech group can be set to orthodox.
BAN - Zulu. (Zulu feels cooler than Bantu. Quite subjective.
MAH - Vietnam. (The Mahratti States don't feel as necessary.)
CYR - Ethiopia. This is not ideal, however, since Cyrenaica will never even be able to declare independence anymore. Also, it will mean that Ethiopia is placed in the muslim tech group with muslim unit graphics.
Is Ragusa really so important?
/Doomie