unfortunately, SOB and SM are so vastly different biologically and fighting strategy wise, they couldn't possibly work off of the same mechanics. A space marine gets half his torso removed and flayed open by a gaus cannon and he'll keep fighting until his adrenaline wears off and then some. Sisters are quite possibly one of the squishier factions. hell, the only way to actually play them anymore in the table top is hit and run tactics, even then you're not going to be too successful. the only ones squishier than them are the DE and IG. Sure the sisters have balls larger than all but Russ's and the Emperor himself, that doesn't mean they're going to live as long as a space marine when charging a tau's railcannons or even eldar weaponry. Hell, most of their forces are deployed against either cults, protecting relics or wiping out some planet deemed "heretical" by the inquisition. there's only been a few times (by comparison to what i previously mentioned) where they were deployed in numbers against some xeno force. a good 70% - 85% of the time it's against some chaos forces, be it cultists or CSM/Lost and Damned or Daemons. if you want to think of them in gameplay terms: Spacemarines are usually the all rounder/tanks. they can dish out damage, also take it. Sisters of Battle on the other hand are more of your DPS members, they have thier flamethrowers and melta's, dealing massive amounts of damage, but also being punched out by things a bit bigger than themselves. they're not as weak as the guard, but no where near being on the level of space marines toughness.
TBH I've never faced Sisters on tabletop and haven't been able to get my hands on their codex yet (though they do have a full codex now), so most of my experience with them is from DoW where they were tanky as hell. I honestly think I had a harder time gunning down Sisters than Tactical Marines, even with a Commissar. They just refused to die. If they really are much squishier ITT then maybe rolling them into/allying them with IG would be a better compromise than SM. They would give IG more melee options than just Ogryns, and people would be able to pick a Sister if they want a bolter or a Stormtrooper if they want a hot-shot lasgun. It would also give IG an excuse to not be allied with Space Marines: they're under orders from the Inquisition, who are being dicks as usual. The problem with a merger is both factions have so many units that some very good units would likely be crowded out, though this would be less problematic if they're separate but allied. Each would be a full faction, they just work together. I wouldn't mind seeing all three factions fully independent, though obviously there are other people who have issues with that.
Trust me, if it were up to me, I'd leave SMs out entirely. IG are not only a much better representation of the Imperium, but they're also better balanced versus the infantry of the other factions. SMs are supposed to be outrageously rare. In my opinion, this MMO would be better with IG instead... But comments like this typically result in an angry barrage of fanboy idiocy: "SMs are everybody's favorite! The game won't sell without SMs! It's not 40k without SMs!" and other such cliches, which probably aren't even true when it comes to an MMO. Unfortunately, it appears that SMs are already inextricably rooted into this game, as you said, whether they fit or not. I would play IG, but I won't play a SM. I'll probably start with Eldar and hope that Tau or DE show up soon.
i think tau is the most likely first new faction they are independent (like the existing 4 factions), they are long range specialists (non of the existing is this) many different units
*shakes hand in a furious and manly way*, your dislike for the Inquisition reflects my own misgivings that's all. But if the SoB are going to be a playable faction the Inquisition is going to make its presence, when playing as a SM the only thing they will get from me is a nice middle finger.
SM are "rare" because the galaxy is huge, estimates at any given time are that there are about 2-3 million SM in the whole Imperium. But they are not rare in "crucial" engagements, if a chapter gets wind of a traitor SM presence in any world they will rush to annihilate them. If there is a big enough war going on you can bet your ass that many chapters will try to be present.
....the reason people say dark eldar is ok is because eldar are already present...and they arent quite as squishy as guardsmen per-person...
They're T3 with one wound, their most common armor save is 6+, second is 5+ (flak armor), their lowest armor save is - (that's nothing, zilch, nada). They only have three 3+ saves and two of them are Pain Engines (monstrous creatures). Their only 2+ is on an Independent Character (who you can't play as, because there's only one of him). They only have two 4+ saves outside of Independent Characters. None of their vehicles have higher than AV11. DE are the epitome of squishy and make Guardsmen all look like Rambo. They basically go into battle in their underwear and rely on speed, high initiative, lots of attacks, and nasty weapons to kill as many of the enemy as possible before they open fire. As soon as anyone starts shooting back they get vaporized. The only way they start to have anything remotely resembling durability is if they manage to wipe at least two units (which typically means killing 20+ models) to pick up Feel No Pain before they die. They're complete glass cannons. I'm OK with them being in, like I said shredding them with a Punisher gatling cannon is sure to be highly amusing, but you can't pretend they have anything even resembling durability.
