AtoMaki said:
To put it bluntly, I'm not sure anymore FFG is actually willing to deliver a ruleset that would support such mixed parties, at least not in a way similar to how GW's Inquisitor game did. And perhaps the majority of (potential) customers even prefers the approach that FFG has taken so far. Think about it - putting Astartes and normal humans on a level where both would be viable character options, even with a focus on combat, would ultimately let Space Marines appear as "weaker" as they are presented in the most popular sources (numerous SM novels), given that they are usually compared to said normal humans. How many Space Marine fans would be willing to accept this, just for an option to have normal people tag along? And given that the Great Crusade as a setting would mostly appeal to Marine fans, thus also rendering them the most likely buyers, this group would arguably also be the likely target audience for an RPG set in this era.
Which brings me to the issue of tie-in options. In the Great Crusade-era, what kind of "above-average normal humans" are there? The Imperial factions of M41 whose members are able to maybe stand up to Space Marines (and thus might qualify as semi-equal comrades to them) do not exist there - in M30 their presence truly dominates the Imperium, and they are doing many of the tasks which are only later filled by the elites of normal humans. The one exception that comes to mind are the SoB-knockoff Sisters of Silence that have been mentioned in one or two books, but from what I've heard they are apparently not allowed to talk - which might feel a bit limiting for a roleplaying game.
I suppose it'd be possible to whip up some special class like an "Imperial Army Veteran" or something, but even then, why would this guy travel with a bunch of Marines and deploy in their battles? (see also Face Eater's post)
It all just seems very … difficult to combine, with many drawbacks and very few advantages. It'd probably be better to just look at the rather popular novels and try to replicate what's in there, kind of like a Deathwatch 2.0. Perhaps the designers can also invent a reason for slightly more variance between squad members - an option might be to make the player characters a Company HQ, with their own NPC Marines and starships, kind of like an Imperial version of the Black Crusade RPG mixed with Rogue Trader and Deathwatch, where the players have to plan and personally lead invasions of entire star systems with the resources provided by their paternal Legion. Maybe FFG could even come up with fluff for a team made up of Marines from different Legions, although I have a feeling that everybody belonging to the same Legion would be okay for the players. Everybody being from the same regiment doesn't seem to be a problem for Only War, at least, and I know that some DW fans are already playing "normal Marine Chapter" campaigns.