Like the developers said, a player can always choose to either stay in a organized squad and tackle objectives or go on their own and do PvE. What I suggested was more variety to free2play players, and the imperial guard, the cultists and skitarii would be good options. Bringing more players to the game is important, giving them some variety would also increase the fun in my opinion.
I think it's needless to say the faction of which i support being added, but as far as balance issues goes and reasons to fight the other factions, the sisters can be worked in. They could have been deployed in order to purge the planet of heresy an xenos filth. the marines and IG would just be unfortunate enough to be in the way when the "exterminatus by flamethrower" order came down. either that or a war of faith on the planet and everything on it was declared. both valid (yet make about as much sense as a 40k order can make) reasons to have them fighting the astartes and IG.
I see no reason for Skitarii. While they need variety I think it removes too much from the idea of Orks and makes things a bit unfair for people like Eldar because at the end of the day they'll have less f2p fans than other factions.
The Sisters of Battle would be my first choice for an additional faction. Now, I can see the difficulty of integrating them with the Space Marines, but I think that cold be solved by having the Space Marines be a friendly faction while giving the SoB their own missions. The SoB could have missions like witch hunts or purges, and then join the Space Marines for the bigger conflicts. I think an expansion probably could be built around something like that.
I'd probably make the Sisters a "female chapter". Yes, they're not real Space Marines, but they're close enough that they'll fit for gameplay purposes. If you choose Ultramarines your armor is blue and you get the normal boring stuff, if you choose Space Wolves your armor and vehicles have wolf fur/skulls all over the place and you get whatever their weapon traits are, if you choose Sisters your armor has boobs and a lot of your weapons get turned into flamethrowers.
unfortunately, you're mistaken on a few points there. sisters are standard humans, who are crushed by astartes when it comes to physical abilities. sure their stregnth is a bit enhanced thanks to the armor, but the astartes have so much more going for them. Not to mention, the sisters have their own convents, which are equivilants of the astarte's chapters. The only thing the sisters crush even the most loyal astartes in is: their faith, which lets them perform "acts of faith" in the emperor's name. But grouping them together and giving them the same stats would make no sense canonically and logically.
I'll post the same thing I did here that I did for another thread that caught my interest. This has to do with the Daemons as a playable race as well as another one alot of people forget (Lost and the Damned.) I honestly believe that will add the Imperial Guard and Necrons as a faction. Whether it will be playable or NPC is up to the devs, judging from the forums most likely playable. Despite the hate that certain people might have for the topic, the lore is going to be broken to make this game. The lore has to be broken to eve make this game feasible. The nearly 7000 people that inhabit this forum are barely going to be even a 1/4th of this games overall population. The devs are using this forum to take in ideas and suggestions for this game. What people are going to want is variety. And by adding the majority of the races through expansions and dlc over time, I think we'll have that much needed variety and flavor. Plus it will help thin out certain populations like the space marines, which the majority of SoB and IG players are residing in. I would love to see the Lost and the Damned and Daemons added as two factions. Preferably in the separate dlcs. Each army is strong in it's own right and adds much variety. And like I said the majority of players love variety ( and evil armies for that matter) With the Lost and the Damned, you can bring forth a horde of interesting units. Traitor Guards Men and Cultist for standard ranged units, Beastmen for strong melee combatants, hereteks for tech priest, rogue psykers, apostate cardinals and priest to match Chaplains, chirugeons to equal apothecaries and medics.Lets not forget mutants that vary in strength, size, and shape, so they could make a considerable force. Let's not forget the vehicles themselves. The Lost have many stolen Imperial Vehicles so it would amazing to see them bring forth corrupted and chaos decorated Leman Russ, Basilisk, Chimera, etc and even more so to see Daemon Vessels such as Stalk Tanks.And we could match land raiders and Imp. Baneblades with our own Chaos Baneblades. And then there's Daemons. The blessed children of the Gods, the manifestations of hjmanities most base emotions. True Angels of the Warp. Blood letters fod melee, Daemonettes for the speed, Pkague Bearers for the endurance, Horrors spewing warp fire from afar. Daemon Heralds leading forth entire host of the Neverborn. We've got juggernauts mounts, Disc of Tzeentch, Blight Drones, Skull CannonsI'll be satisfied if they abide by the fluff at least 50% when it comes to the gameplay, but I do believe that they will add all of the races.
Um...I never said anything about their strength or abilities. I know they a good deal weaker than the Astartes. What I was suggesting is that they have separate missions and mission types from the Astartes, barring large-scale conflicts (like war-sized faction battles or certain group events). Then, for pretty much the only time, the SoB and any other imperial factions would fight alongside the Astartes. They wouldn't be equal to them, the lore could be preserved, but they could perform their own roles in big battles.