There's no such thing as a "fluff based combat system". At the end of the day we're going to have to make guesses about where things stand and where they should stand, then assign stats to reflect those opinions. "The fluff" isn't some giant, monumental physics simulation where GW checks every tiny detail for absolute accuracy. It's a patchwork collection of what is essentially fanfiction written by dozens of authors who all like different factions. It's rife with bias, handwaving, mary sues, and plot armor. A determined fan sifting through all that could easily craft an argument that THEIR faction, no matter which faction it is, should absolutely curb stomp all the others without breaking a sweat. That's more suited to a singleplayer game than an MMO. You would think people would know this after Kaldor Draigo and the Necron-Blood Angels tag team incident.
There's enough on sites like 40k wiki and Lexicanum to build a solid framework with *accurate* tech and stuff. Yeah, it's spotty in places, but as long as you don't have to say "Man, those .75 caliber high explosive, armor piercing, rocket propelled bolter rounds sure are powerful, I guess we should make it easier for _____ by adding this or making a mechanic to nerf it" then it's good. You don't need some complex system to make things "fair" when as stated above, you can work as a team and get stuff done.
so ? that doesnt meant that there arent some established things like, how powerful a marine boltgun is, or what a plasma pistol can do to a target etc... if all else fails, look at the current TT stats. you have to decide at some point what to use and believe and what not.
The RPG is actually a much better thing to use than the TT. while I enjoy the TT and will until the end of days, the RPG is much more detailed and has that sort of thought that has gone into it to make it make sense. And it can be more 'true' as it doesn't need to worry about balancing a pretty limited range for stats and balance between armies.
Look at lore where it makes sense to look at it, TT itself differs so much from the lore for gameplay balance. The same way this game should do its own thing, see what works, experiment, look at what feels good and continue with that, not feel trapped by the TT and codices.
I am also finding it silly that people want exact replicas of TT or WH40k lore imprinted into this game. It is as if they have never considered that the game should be FUN FIRST and then lore accurate.
Help me if i am getting this right but the class selection will be like star wars battlefront 2 where you pick your class when you enter battle and when you die you can selected a different one??? Because for me that would be weird......