From what i'm aware, there were initially plans to make a fourth "Android" resistance faction lead by either Julien, or a copy of him in some form. They were intended to be the foil to the Templars in some sort of "mind Vs Matter" thing similar to how we get a mission depicting the rivalry between the Skirmishers and the Reapers.

There were also plans for a fourth chosen, this one being more of a grenedeer-type with weapons that would fit that class, meaning each class of Soldier would now get a Chosen-weapon assigned to it.

All of this unfortunately had to be cut for time during the launch of War of the Chosen, though you can still find a prototype for an Android cutscene on youtube.

So i'm surprised that nobody (to my knowledge) has ever tried modding these concepts into the game, is there something holding it back from that? Seen plenty of other resistance-faction or resistance-soldier mods, so i don't think the Androids themselves would be an issue, maybe the Chosen is more complicated?

Personally think the chosen would be female, as I've always subscribed to the idea that the chosen were made by tampering with Annette Durand and the other three Furies, which in total add up to two men, two women, and even the classes lining up with Annette being Heavy, Matthew being Sniper (Hunter), Said being Support (warlock), and Fatima being Assault (assassin)