I don't see a Inquisition faction as being viable. Inquisitors and most of their henchmen are too few to warrant being playable classes in EC. Inquisitors could maybe be a Hero class, as they're not much rarer than Farseers, for example. Their henchmen could be elites that you don't spawn all the time, but I wouldn't want to see Crusaders and Arco-flagellants as baseline classes that are deployed in massive numbers.

What I see as viable is the Inquisition being involved in virtually any Imperial faction that could be in the game. But I see no reason to put a "Inqusition faction" sticker on any of them.

With that being said, I also don't really see any reasons against making Sisters of Battle a faction of their own. Why do you, Makeka, think that they shouldn't be a faction of their own?

Edit: You beat me to it. -_-

Ok, that is not a bad reason at all. A Witch Hunters faction would work for me too, but I feel that having Inquisitors and troops from all three Ordos wouldn't be a good idea. They generally have different objectives and don't work together.

That's kind of like saying Space Marines are a missed opportunity to bring in the Inquisition, though.
Inquisitors can work alongside any and all Imperial armies. Being reminded of the Witch Hunters Codex, all I can say is that the approach you suggest would end up diminishing the Sisterhood, and I don't agree with the concept of marginalizing an already marginalized faction further. In fact, what you are proposing is worse than C:WH in that Sisters would only end up being ~1/4th of the faction, and the massive amount of units you suggested would lead to feature creep and extended development times.

If we were to look at it from that angle, the game may just as well have offered Sisters as the alternate-gender option for Space Marines and be in from the start. In fact, I would have preferred this approach, both because it would have made sure that SoB are in right from the start and comparable in battle prowess to the Astartes, as well as because this would let them appear more independent than if you were to shoehorn them into an "Inquisition" army. In terms of exposure and popularity, they may have also benefited from the role the Space Marines have for the fans of the franchise, perhaps resulting in new SoB fans even outside this game.

It was by no means to diminish the presences of the sisters I merely thought it would fit well together as I mentioned before. I see your point and my idea might do more harm then good despite my intentions.

I disagree on the notion that they should have been a female option for the Space Marine. Are you not contradicting yourself in that regard? Would that not be a disservice to the SoB? To let them simply be a reskin for Space Marines? Them having Inquestion units was merely meant as a supplement to their ranks(thou it might have come out in a negative way). To not have them be their own faction(with or without supplement) and own gameplay style is unacceptable.

I see nothing wrong with a number of Inquisition units supplementing a SoB class rooster in EC. I wouldn't even mind if SoB were part of the same faction as LSM or if they were perhaps mashed together with the Imperial Guard. I don't even care about having a separate faction council and command structure, although I'm of the opinion that it would certainly be better if they had such things.

Anyway, whether the faction is called Sisters of Battle, Witch Hunters, The Inquisition or even Imperium of Man is not a detail I'd fret over too much. If the good sisters have a satisfactory class rooster of basic, elite and hero classes I'll be satisfied.

Of course, it would be preferable if they were a faction of their own. But given the circumstances, I'll take what I can get.

I guess it's a matter of how you see them - for me, the appeal of the Sisters has always been chiefly their style. The look of their armour, the background of the army.

The Sisters are, to quote GW, "organised along similar lines as the Space Marines", which becomes obvious once you look at their core army: Dominions as Tactical, Seraphim as Assault, and Retributors as Devastator Marines. Aside from their visual appearance, the biggest difference is their lack of genetic enhancements, balanced by access to Acts of Faith. My idea would simply "abstract" this difference in a way that it converts the "efficiency spike" triggered by an Act of Faith into an always-on passive ability that gives them the same stats as Marines.
Veterans of the tabletop might even remember that something like this was already in the game back when Sisters were still using Sacred Rites before each battle for a permanent bonus. Acts of Faith and their temporary bonus did not exist until 3rd Edition.

Yes, it's a "dumbed down" system, but as I said my main concern is style/feeling - and truth be told I doubt the mechanical sameness would actually attract much attention in an MMO that sees hundreds of characters shooting at each other. At least not any more than Devastators repairing vehicles...

I've become skeptical in regards to any further faction being added to EC, and I'm even starting to think four is too much already, but I like to think the above might have been an option that is comparatively easy to implement and non-intrusive. Similar to Lelorelyn, I'd "take what I can get", I am just willing to go as low as making Sisters "Marine reskins" .. though I'd still regard this as more faithful to their role as an independent army than making them sub-classes of a different faction.

It would have been a safer alternative - both to Sisters possibly never making it into the game, as well as an interpretation of Acts of Faith that goes against my own. Personally, I can do without Sisters casting D&D-style magic like they do in FFG's RPG; I much prefer GW's more ambiguous version.

sob and ig should be own factions not "forced allied" to anyone

the war council can ally with sm if the want.
but the game should not force you

That's true about the equal migration. I'm playing as Chaos now but if and when the Tau get included, I'm hoppin on the Greater Good.
The races i can see becoming playable are the SoB/Inquisitional force, Dark Eldar and Tau. The races i'm iffy on are the Necrons and IG.

okay, and how would they be able to explain the SoB fighting 5 space marine chapters without having the inquisition erase them from existence? come on now.

The ecclesiarchy wants a relic from Arkhona, SM chapter says that relic is ours, more than enough reason for them to fight, also the SOB have fought before against the wolves.

i don't think I could ever accept that as canon, if that were the case we would have to accept all of the abomination that was soulstorm as canon, and I don't think ANYONE here is dumb enough to want that.

You'd practically be starting a second heresy era if two imperial forces of that size were to duke it out over a planet. Possibly even three if the imperial guard were thrown in there as a separate faction.