I ve added a scientific leader trait into the game, there was something similar in Civ 3, don't know why they did not include it in Civ 4.
The bonus i added are :
+3
/ city.
Half production cost for library, university, laboratory.
The result is interesting. If someone is interested, i can post a link to the modified files.
Modifications in Civ4TraitInfos.xml :
<!-- BEGIN -->
<TraitInfo>
<Type>TRAIT_SCIENTIFIC</Type>
<Description>TXT_KEY_TRAIT_SCIENTIFIC</Description>
<ShortDescription>TXT_KEY_TRAIT_SCIENTIFIC_SHORT</ShortDescription>
<iHealth>0</iHealth>
<iHappiness>0</iHappiness>
<iMaxAnarchy>-1</iMaxAnarchy>
<iUpkeepModifier>0</iUpkeepModifier>
<iLevelExperienceModifier>0</iLevelExperienceModifier>
<iGreatPeopleRateModifier>0</iGreatPeopleRateModifier>
<iGreatGeneralRateModifier>0</iGreatGeneralRateModifier>
<iDomesticGreatGeneralRateModifier>0</iDomesticGreatGeneralRateModifier>
<iMaxGlobalBuildingProductionModifier>0</iMaxGlobalBuildingProductionModifier>
<iMaxTeamBuildingProductionModifier>0</iMaxTeamBuildingProductionModifier>
<iMaxPlayerBuildingProductionModifier>0</iMaxPlayerBuildingProductionModifier>
<ExtraYieldThresholds/>
<TradeYieldModifiers/>
<CommerceChanges>
<iCommerce>0</iCommerce>
<iCommerce>3</iCommerce>
<iCommerce>0</iCommerce>
</CommerceChanges>
<CommerceModifiers/>
<FreePromotions/>
<FreePromotionUnitCombats/>
</TraitInfo>
<!-- END -->
Also don't forget to modify the Civ4BuildingsInfos.xml to add the production bonus for the buildings :
...
<ProductionTraits>
<ProductionTrait>
<ProductionTraitType>TRAIT_SCIENTIFIC</ProductionTraitType>
<iProductionTrait>100</iProductionTrait>
</ProductionTrait>
</ProductionTraits>
...
And to add the proper text in the text files :
...
<TEXT>
<Tag>TXT_KEY_TRAIT_SCIENTIFIC</Tag>
<English>Scientific</English>
<French>
<Text>Scientifique</Text>
<Gender>Male</Gender>
<Plural>0</Plural>
</French>
<German>
<Text>Scientific</Text>
<Gender>Neuter</Gender>
<Plural>0</Plural>
</German>
<Italian>
<Text>Scientific</Text>
<Gender>Neuter</Gender>
<Plural>0</Plural>
</Italian>
<Spanish>
<Text>Scientific</Text>
<Gender>Neuter</Gender>
<Plural>0</Plural>
</Spanish>
</TEXT>
<TEXT>
<Tag>TXT_KEY_TRAIT_SCIENTIFIC_SHORT</Tag>
<English>Sci</English>
<French>
<Text>Sci</Text>
<Gender>Male</Gender>
<Plural>0</Plural>
</French>
<German>
<Text>Sci</Text>
<Gender>Neuter</Gender>
<Plural>0</Plural>
</German>
<Italian>
<Text>Sci</Text>
<Gender>Neuter</Gender>
<Plural>0</Plural>
</Italian>
<Spanish>
<Text>Sci</Text>
<Gender>Neuter</Gender>
<Plural>0</Plural>
</Spanish>
</TEXT>
...