How many of factions ( major or minor ) are required in a mod?

[The Great Khan of Rome]

I'm asking this since I'm starting to mod Attila's map and i'm asking if you need to have any sort minor faction. I want all the playable factions to be major, but the only non-playable faction is the rebels.

[Augustusng]

I think you can have as many or as few major or minor factions as you want. Just be careful with all the startpos changes you'll have to do for that. It's a lot of work if you want to change the ownership of many regions.