Here we have definitions of the various Forms of Government. For each type it is required that you define the number of years between allowed domestic policy (DP) changes (adm_efficiency) and which forms of government you are allowed to convert to (allowed_conversion). Under the latter you also define how much stability a conversion will cost.
administrative_monarchy = { adm_efficiency = 12 allowed_conversion = { administrative_republic = 2.0 absolute_monarchy = 1.0 } production_efficiency = 0.05 }
In addition, there are a number of optional declarations you can use. The maximum_policy and minimum_policy sets limits on certain DP sliders. You can only use one policy slider restriction for each government type.
If you set republican_name = yes, the monarchs will be given with given and surname instead of just first names with numerals, as discussed under monarch names.
Setting royal_marriage = no means that the country cannot enter royal marriages. In difference from the other declarations used in the common files, this one defaults to yes and is only needed if you want to set it to no.
Lastly, religion = yes is used for special religious types, like the Papacy and theocracies (archbishoprics). It is used to prevent forced religious conversion as the result of losing a war.
The titles of the rulers are defined based on the government type name, and is found in the localisation files. The official types are located in text.csv, like the example from above:
administrative_monarchy_ruler;King;Roi;König;Król;Rey;Re;;x
Modding government types
As it is in the current version, the names are flavoured based on culture [or possibly country tags?] (hence e.g. the Sultan of the Ottomans rules a Despotic Monarchy even though the ruler of that government would normally be called a King). The names of a ruler are defined in the localisation file, for example:
despotic_monarchy_ruler_russian;Csar;;;;;;;x;
As with most other things in EU3, you can change, add or remove as you feel. And as other edits, it is important that you use exactly the same name in the other game files as you define here.