[quote=@tundrafrog1124]
Would it be possible for my character to lead a faction of scourges and drukhari converts? They could reside on Yonah already, perhaps having come to the world seeking alliance with the Exodites or sheltering there from other Drukhari. 


Or they could be fleet based. Whichever works for you. 
[/quote]
So, regarding the Ynnari, the force has been sent by Yvraine herself, the Emissary of Ynnead, and the Ynnari Warhost will be lead by my character. Ynnari Warhosts are often comprised of squadrons of all sorts of Aeldari factions, including Drukhari, so your character could be the leader of the Drukhari detatchment of the Ynnari Warhost, if that makes sense! If that's the case, however, then your character and those in their service would have come to Yonah with the rest of the Ynnari force, through the Webway Gate. 

[quote=@tundrafrog1124]
In terms of scales for factions are we doing hard numbers? Or just general estimates
[/quote]
For the entire factions, general estimates; but if your character leads a squadron or a division of other Aeldari, I'd say harder numbers! You can always edit that into the character sheet skeleton. (I will likely be making a few edits to it myself, including Wargear and the like)