Any kind of PvE 40K MMO would have an incredibly steep hill to climb in order to sell that game to players, regardless of how you want to theorycraft any potential PvE design parameters.
Says who?
Lets see:
-Space Marine; Single player game. I didn't buy it for the multiplayer portion. Also, one of the features asked for the most was the Co-op campaign that never came, instead we got the exterminatus thing. To be honest with you? All of my friends that have played SM when asked about a 40K MMO, want more SM, but able to co-op it with friends and go on more missions. With the option to play as Chaos and have locations along their way where they can duke it out against space marines and vice versa.
-Dawn of War series, 1 and 2. Doubt multiplayer was its strength. It sold on its single player campaigns. I only played multiplayer with my buds. Neither of those games were anything like Warcraft of StarCraft in terms of multiplayer community. Why do I say this? If the common consensus is that PvP is 40K's strength in the PC gaming world, what better source to use than the Dawn of War games. I never felt that multiplayer was ever their greatest strength and main reason people bought those games, I could be wrong though.
I have played the RPG, and we have played PCs versus PCs. We had an issue with too many people showing up to smash everyone into a single group. I mean, they make all kinds of references for the RPG that you can do whatever you want, and like most PnP RPGs if you are limiting yourself to what you say above - playing a retinue and doing PvE - then that's on you, honestly. It's no different than old D&D groups that tried to run two separate and opposing groups when they had an excess of players and some wanted to play evil characters. We did that some back in the day and it didn't go any worse than the standard RPG games went. If you're limiting yourself to playing the RPG as a psuedo-PvE encounter then I don't know what to tell you, other than it is a horrible argument to try to support a PvE 40K MMO with.
None of those games are designed for that, neither is D&D 3.5+ . That sort of play is discouraged actually (see the numerous D&D insiders). If you and your group played that way, more power to you guys. Normally around here, you either got warned or kicked from the groups. The official D&D games didn't allow players doing that either. All of the groups out here that are running the dark heresy series of RPGs (Deathwatch, rogue Trader, etc) have a single DM and a group of players around them, all working for the inquisitor or what ever. This is besides things like hero arenas and such.
The reason why I threw in the dark heresy examples was to show that a co-op MMORPG with a lot of depth is very feasible, optional Pvp thrown in.
Actually, be interesting to take a survey of the local gaming groups to see what their take on it is, I can easily do that. We have a hobbytown that rakes in about 30-40 every Friday night for gaming, and another store that has a Wednesday campaign. Back when I had my own store, we talked the same BS we're talking about right now, a 40K mmo. Most of the hype back then was around the Warhammer fantasy one by mythic. Rarely did any of the numerous neckbeards ever say "it must have pvp at it's core and pvp must be meaningful". The main talk back then was a game similar to Inquisitor, where all players were imperials banding together.
Now, don't get me wrong, I don't have a problem with PvP. Hell, I got no problem with Planetside in 40K land, I'd actually prefer that. I just don't understand why you guys say that PvP has to be at its core. When you say 0.0 space, I translate that to mean: I -must- PvP to get the better shit. Unless you guys mean just the mechanic and not the risk-reward part (which then defeats the whole purpose).
I just don't see GW taking a risk (or any small company licensor) taking a risk on something like that. GW already has a track record of catering to the WoW sort of game composition:
-Mythic's Warhammer Online
-The original warhammer online was going to be that everyone was Empire (and allies of the empire), fighting the various denizens of the setting. Keep in mind that this first iteration of the game was almost entirely funded by GW and they had both hands in the cookie dough.
-In White Dwarf 300 (if I recall correctly), GW themselves said that "Movie Marines" (i.e. the concept of Space Marines found in the novels and fluff) is not conducive to proper balanced gameplay and that concessions have to be made in the spirit of sportsmanship and fun. Be interesting to see how that idea translates to the rest of their IP's and MMOs derived from them.
I'm not saying the game should ONLY be PvE, or PvP, I'm just playing devil's advocate on behalf of Grandma Wendy knowing how they prefer the big bucks.