Lets face it the bolter is not going to be fluff accurate in any game, the gun is just to overpowered to be done justice in a game that doesn't base its combat around one hit kills. The bolter fluff wise is an unstoppable force that literally kills anything but carnifexs in a few shots. Now with that in mind the guard can be a feasible army if they have the same in game focus that they do on table top. Their main weaponry that does serious damage is their tanks. Hell entire regiments are dedicated solely to tanks with no infantry to speak of. If they field tanks and veterans in gameplay as playable you have a well balance, maybe even overpowered, army compared to wank marines.
So we were sorta just talking about this in a sideways way in another thread... Just throw the Inquisition, IG and Sisters (who could stand alone technically I guess), in one lump, and bam, there's a side. The Inq needs the support, so the high ranking Sisters (pick an Order) and IG could justify that I suppose. Maybe some Death Korps or Catchan. I dunno. A mixed bag side with their more powerful options being made progressable (not a word). No clue what was really mentioned above... stopped reading after a few pages... WAY too many pages. Probably a silly idea, but hey, it would fit the Lore. Mostly. I think. *shrug* *edit Thank you Don Lingo for reminding me of the Grey Knights too! Throw them in!
Strangely despite my love for the guard.... I like what you just said. The inquisition could be an army on their own seeing as they field stormtroopers, sisters, and inquisitors themselves. This could really be the strong not squishy army type with the playable classes that fit what me as a Guard player want in this game.
Don't forget Grey Knights, although they'll probably never make it in for balancing reasons. They could just play the part of the "hero" a la Star Wars Battlefront II. Best X amount of players in the faction get to use them. Wouldn't be half bad.
Yeah it's starting to seem, at least from what I've seen posted here, that the lore is a bit uhmm...conflicting on things lol. And yeah I really don't see the harm in fielding them in with the Space Marines if they want to go that route. Seeing an army of them dying each day would be weird, as from what I understand, Space Marines are somewhat of a more limited population compared to other races.
the problem is that a bolter would kill a marine in one hit if it were true-to-lore, and in, say, five hits if it wasn't. and that thing fires fast, so thats about a second to kill a guardsmen.
on the other hand, sisters could be lumped in with the space marines. then the eldar won't be the only faction with females. the guard don't really have bolters and power armor, so the sisters wouldn't really fit with them thematically
I'd rather have Imperial Guardsmen beating Space Marines in 1v1 combat and carrying heavy bolters on their own with jump packs than have Grey Knights in the game. It's an even WORSE balancing nightmare.