Thanks for answering!
Edit: I decided to give a little feedback on what you said and elaborate what i mean... I had no idea it would become such a large rant. So I apologize in advance.
Yeah the naming conventions is just a "marketing" thing if you will, there is no perfect way though the vanilla game's distribution of these factions but in my opinion the base Attila game was made for only 7 categories and 6-7 factions in each category otherwise things will "stick out"
So... if you guys like keeping the factions and their categories within the margins of the menu art then I humbly suggest the following breakdown. I could not find your playable faction list so I made do with an image.
The only issue with this suggestion is the "Other Barbarians" because that term is not accurate and the culture bonus might not be representative either.
More importantly regarding the economy and their extremely large numbers... personally I don't think just having large numbers thrown at you makes you feel like you are running an empire.
Excuse my ignorance but I am sure you guys have probably poured hundreds of hours over how the economy, upkeep, resources and cities should function.
One of the things I think is completely missing in TW games are cashflow negative cities.
Thats why the Western Roman Empire needed its African holdings or Eastern Roman Empire's help not only for food but riches as well. If the player decides to make a certain city Military oriented it should drain food and much more money. Industrial cities drain a lot of food and so on. Meanwhile there are some settlements that just have no capability of being industrial or a great market place due to lack of nearby resources or trade routes.
In total war we have never had tough decisions like "Do I really need this region? it sucks!" or "I can't afford the secondary costs of these buildings... my current region can't support the food cost I need Egypt or North Africa to feed my industrial cities. All new territories are positive cashflow ranging from wealthy to really wealthy, there is just no downside besides some negligible public order penalties. No tough decisions needed for a certain treaty or territory.
The base Attila game had some nice mechanics like local food shortage/sanitation to cause public order penalties. Its a great idea, historically Rome at its later periods could not feed itself so most of the food was imported from far away... Now I don't think rome was perpetually unstable because they imported food rather than ate locally so this vanilla system has its limitations but if you guys can enhance this vanilla feature I think it can greatly help you guys achieve the "tough economic decisions" required for running an empire.
Personally I feel these types of decisions and hard economic choices are what makes you feel like truly running an empire. Situations where the player says to themselves "Jesus Christ I need Egypt for its food or I am screwed" rather than "where do I feel like conquering next?"
If you guys can manage some sort of diplomacy options for one faction to send "food" like through trade that would be truly amazing. This allows the players more interested in diplomacy and client state/satrapy creation a chance to stay in the game rather than conquer everything to stay alive.