I think it's safe to say that we all know what 40K is. The popular miniature based game is only one of the best known games around aside from D&D. Fantasy Flight Games offers Dark Heresy, Deathwatch, Rouge Trader and Fantasy Rolepaly, role playing games from the War Hammer universe. They also offer Chaos of the Old World and Horus Heresy, board games from the War Hammer universe. Maybe the last thing the world needs is another 40K game but here goes anyway.
How about a 40K board game that deals with a conflict on a planetary scale? Imagine Axis & Allies meets 40K. Bascially the board would be the map of some planet in the 40K universe. It could be a hive world covered in vast cities or some far flung feral world. Anyone who has ever played Dark Heresy or read any of the 40K novels knows there are a myriad of world types to draw from. This also leaves open the expansion of the game by releasing new map boards with different worlds. I personally envision the game coming with a Space Marine army supported by Imperial Guard and possibly a Chaos army or Orc army as the opponent. Again this leaves open the possibility of expansions. Other armies could be released such as Necrons or Eldar and even expansions for the Marine and Guard armies. Obviously the scale of the miniatures used would need to be much smaller than standard 40K tabletop mini's. I'm thinking something along the size of A&A or Runewars.
The board itself should also include orbital zones above the planet. This is where an attacking army would place their vessels full of assault troops before sending them to the planet below. Some scenarios could even feature both armies arriving by spacecraft to lay claim to some uninhabited world. Regardless of the scenario, the point is there would need to be orbital zones above the planet incorporated into the game. The primary object of the game, however, is to lay claim to the planet itself and that will of course mean an epic struggle on the ground. In my personal opinion the key here is to offer a game with a lot of miniatures to field both (or even more than 2) armies. A board game about a planetary wide epic struggle that only has 50 to 100 miniatures is a let down, at least to me. I would think something along the lines of 300 to 500 miniatures at a minimum would be better suited and with expansions the count could go up from there.