It would not be impossible for the Aestari to have a faction but I believe they form the Neutral “faction”, don’t they ?
Anyway, having read through the whole valaible lore right now, carefully looked at the map, there is little to no possible factions aside from the Aestari and Inxikrah. Unless they add more lore. Again, that’d be strange. If I got it right, factions compete for the control of the Monolith. Which is in the middle of the world. Every other faction comes from the surrounding continents. My point is, lore wise, everything has been explored. And even foreshadowed, Silverbeak is mentionned in one of the chapters, which were written before Shim’zar. At best I think they could add more Generals, new BBS could be the sparks of new playstyles. Unless they add actual Neutral Generals. And Neutral Spells, which would still be Neutral exclusives. But it really wouldn’t work well. Neutral units aren’t really meant to synergise together.
And an other thing, the mandates are only “laws”, how to base spells out of it ? And the weeping tree is dead. That’s why the Monilith was built. So unless the actual game is based later in the lore, the weeping tree is dead. Nothing to do with it.
I just noticed I talked more about lore than anything else. But I think it’s important, everything is based off of it.