I have a document outlining several worlds in the Markayn Marches I'd be happy to share, now that Green Knight has started on it. It's written from the perspective of an Imperial Navy officer briefing on the strategic importance of the worlds (I was going to use it for a BFG campaign), but has a variety of socio-political commentary in there too.
Did the Alien Hunters thing ever take off? If not, I'd be more than happy to write some materials on potential Ordo Xenos factions. Mainly split around whether to kill or use. I haven't mapped these out too much, but I expect some overlap with the main factions detailed in the Inquisitor rulebook.
I'd also be into detailng some of the more alien xenos. I've been dying to run a short game with the Umbra on a Charter vessel being mistaken for dæmonic activity. That and dealing with the other minor races present in Xenology, and possibly the Lacrymole.
I've also noticed the depressing line in DH 1e saying that no one could ever record all the eccentricities of the Ordo Calixis. Do we have enough material to make a start on this sort of thing? I admit I haven't got many sourcebooks to go on, bu7t a compilation of ideas and a sketch of the politics would be a start, I think.
Any of these sound appealing? Let me know and I can make a start in the next few weeks.