A 40K RPG would be fantastic. One done by Bioware? Not so much. I can already picture the sexually promiscuous space marine conquering the galaxy while sleeping with a procession of orks, tyranids and tau...
Don't forget crushing every demon prince ever, finding every missing Primarch (one turns out to be female and will be a romance option), prevent the 14th Black Crusade and unite every race against Chaos.
...Yes, even the tyranids.
...And the necrons. Especially the necrons.