For the expansion of factions, I think you should consider making them like WoW talent trees and each Faction is a single class tree. Then you'd have the mechanics of resetting your skill tree etc

The other option is, the factions you could think of for this, we'll call it a Chapter, Chapter 1, this is Branch 1 with 3 sub branches Sabrask, Miridian, Aeros. Chapter 2 is essentially the next season for the battle pass and you unlock new abilities with each new battle pass.

But you really need to decide or better communicate the intent behind the factions because right now, it's sort of background noise.

Either they are a huge part like factions in Helldivers 2 or they're your actual character type you choose and your skill tree defines how you play aka Guild Wars 2.

Then you need faction levels, seasonal wars, faction skill trees, loadout bonuses/faction equipment perks, and maybe even allowing players to swap factions for a season to spice things up. Their character just becomes reskinned to the matching faction color but the model is the same as their faction.