While it would be awesome, there would be an issue with it.
If the series was made with even a PG rating in mind, it would ruin the image that GW has set up, with war everywhere, hope is gone, and that most common deaths able to be experienced in the 41st millenium would be way too gruesome to ever think of hinting at.
Or, if the series was made for the most mature audience you can think of, it will never reach the amount of potential buyers that GW would probably want from such a series, due to either, not being allowed to watch it, not wanting to watch it, or be on so late/so early that no one is awake to see it.