Hey Kareal!

I don't personally have time I can "allocate" to make this example mod, however these are the data types that you will need to modify if you want to create a new faction:

<!-- Faction definition (listed both in the Faction DataType, via an ExtraType, and in the MajorFaction DataType) -->
<DatabasePlugin DataType="Faction, Assembly-CSharp">
<ExtraTypes>
  <ExtraType DataType="MajorFaction, Assembly-CSharp"/>
</ExtraTypes>
<FilePath>Simulation/Factions[*].xml</FilePath>
</DatabasePlugin>

<DatabasePlugin DataType="MajorFaction, Assembly-CSharp">
<FilePath>Simulation/Factions[Major].xml</FilePath>
</DatabasePlugin>

<!-- Faction traits (affinity, mapping, population trait, etc.) -->
<DatabasePlugin DataType="FactionTrait, Assembly-CSharp" Priority="20">
<ExtraTypes>
  <ExtraType DataType="FactionAffinity, Assembly-CSharp"/>
  <ExtraType DataType="FactionAffinityMapping, Assembly-CSharp"/>
  <ExtraType DataType="FactionPopulationTrait, Assembly-CSharp"/>
</ExtraTypes>
<FilePath>Simulation/FactionTraits.xml</FilePath>
<FilePath>Simulation/FactionTraits[*].xml</FilePath>
</DatabasePlugin>

<DatabasePlugin DataType="FactionAffinity, Assembly-CSharp">
<FilePath>Simulation/FactionTraits[Affinity].xml</FilePath>
</DatabasePlugin>

<DatabasePlugin DataType="FactionAffinityMapping, Assembly-CSharp">
<FilePath>Simulation/FactionTraits[AffinityMapping].xml</FilePath>
</DatabasePlugin>

<!-- Population definitions, and population traits. -->
<DatabasePlugin DataType="PopulationDefinition, Assembly-CSharp">
<FilePath>Simulation/PopulationDefinitions.xml</FilePath>
</DatabasePlugin>

<DatabasePlugin DataType="PopulationTrait, Assembly-CSharp">
<ExtraTypes>
  <ExtraType DataType="PopulationModifiersTrait, Assembly-CSharp"/>
  <ExtraType DataType="PopulationCollectionBonusTrait, Assembly-CSharp"/>
</ExtraTypes>
<FilePath>Simulation/PopulationModifiersTraits.xml</FilePath>
<FilePath>Simulation/PopulationCollectionBonusTraits.xml</FilePath>
</DatabasePlugin>

<!-- Descriptors (all the gameplay effects!) -->
<DatabasePlugin DataType="Amplitude.Unity.Simulation.SimulationDescriptor, Assembly-CSharp-firstpass">
<FilePath>Simulation/SimulationDescriptors.xml</FilePath>
</DatabasePlugin>

<!-- Galaxy generator, there's an entry for "which star type should be spawned for each faction" in the vanilla XML -->
<DatabasePlugin DataType="GalaxyGeneratorWeightTableDefinition, Assembly-CSharp">
<FilePath>GalaxyGenerator/WeightTableDefinitions.xml</FilePath>
</DatabasePlugin>

<!-- Ship design definitions, hull definitions, templates and other stuff, if you want your faction to have new ships! -->
<DatabasePlugin DataType="ShipDesignDefinition, Assembly-CSharp">
<FilePath>Simulation/Battles/ShipDesignDefinitions[*].xml</FilePath>
</DatabasePlugin>

<DatabasePlugin DataType="HullDefinition, Assembly-CSharp">
<FilePath>Simulation/Battles/HullDefinitions.xml</FilePath>
<FilePath>Simulation/Battles/HullDefinitions[*].xml</FilePath>
</DatabasePlugin>

<DatabasePlugin DataType="ShipDesignTemplateDefinition, Assembly-CSharp">
<FilePath>Simulation/Battles/ShipDesignTemplateDefinitions.xml</FilePath>
</DatabasePlugin>

<DatabasePlugin DataType="FleetNameMappingDefinition, Assembly-CSharp">
<FilePath>Mapping/FleetNameMappingDefinitions.xml</FilePath>
</DatabasePlugin>

<!-- GuiElements (some extra ExtraTypes may be needed depending on your changes) -->
<DatabasePlugin DataType="Amplitude.Unity.Gui.GuiElement, Assembly-CSharp-firstpass">
<ExtraTypes>
  <ExtraType DataType="Amplitude.Unity.Gui.ExtendedGuiElement, Assembly-CSharp-firstpass"/>
  <ExtraType DataType="AffinityGuiElement, Assembly-CSharp"/>
</ExtraTypes>
<FilePath>Gui/GuiElements[*].xml</FilePath>
</DatabasePlugin>

<!-- Localization -->
<LocalizationPlugin DefaultLanguage="english">
<Directory>Localization</Directory>
</LocalizationPlugin>

You can see it's... quite heavy.

We also currently have an issue with the loading of custom FactionAffinity and their AffinityGuiElement, which requires you to add your AffinityGuiElement directly in the game's files, in GuiElement[Affinities].xml.

If you're still interested in making this mod and need some help on the technical aspects, I'd be happy to answer your questions!