I would have played it even if it was a WoW clone.
I wouldnt care whatsoever. I would have played it if it was almost identical to WoW in mechanics, art style, EVERYTHING. Warhammer 40k is just... Awesome. And, as you said, tailor made for an MMO. Everything goes in that universe. Hell, they would no suffer the same fate as WoW has, Expansion Fatigue. In a universe where they can literally get away with blowing up an entire planet (Hello Exterminatus) add another planet on a whim (Planets coming back from the warp) have giant spaceships just float into a system, filled with daemons of all kinds (Hallo Spacehulks)... Seriously. I hope that one day a decent team gets hold of the IP and finally makes a decent Warhammer MMO.
*sigh* I wish Warhammer:Online (Or WAR) was not such a flop. I got it on day of release. It was strange though. I loved every element that went into the game but could not keep playing it. It looked better than WoW, had more interesting lore than WoW, had some really awesome ideas behind it, the PvP was more enjoyable than WoW. Seriously, all of the parts added up to a WoW killer if taken by themselves. But added together? Somehow it became Bland McBlanderson. And then I went back to WoW.
I guess its a good thing that there aint a single MMO on the market that can keep me interested for upwards of a week. What with Uni and whatnot, Lol.