The thing about publishers, is more often than not, they have a say in the game's development. Its like shareholders. you cannot ignore them compltely
Square tries the "dark and edgy" action thing all the time, but their consistent character design basis of Forever 21 coupled with writing that is B-movie at best and Twilight-tier trash at worst sinks that ship while it's still in the dry dock, every single time. I would honestly prefer that Square just stick to honest dissemination of information/marketing regarding the game (lol Tomb Raider amirite?) as per the direction of the dev team and leave the business of making games about the 40k universe to those who give a shit about the franchise as a whole. As others have stated, Square fans =/= 40k fans, and that GW ultimately controls and cares about what happens with games built around their IP (some of the recent games releases make me wonder though). If Square up and decides that all the characters in EC should be Squeenix pretty, I'm positive that literally everyone from both Behaviour and GW will respond with a resounding, "LOL NO".
That's what I mean though. I don't feel like they would have agreed knowing those constraints. This might be them trying to get an actual foot in the door for darker shit. I know I'd be skeptical of a SE game that was supposed to be dark and brutal. They also just aren't as big as they used to be. They might want some fresh fans.
They wont have the power for that, the only people that tell BE on what to do withing their game is GW, Square are just here to publish the game, to get it from the shelves to your pocket.
What's wrong with square enix? They did kingdom hearts . they might even give 40k there graphics engine one day. Also its be that's making the game.
Its own graphics engine? ooooh tempting, im also tempted to make a thread about what we should call it... WARengine? Nah too cheesy...