One rather big problem is that your entire book is based one someone elses IP. And "the company who shall not be named" have done a LOT of work, across the world, to safeguard thier IP. Afterall, its their biggest asset.
Take a look at Osprey and see how their authors go about producing books on modelling WW2 tanks, as they base a lot of those books on SPECIFIC companies kits, so that may be a start...
And thinking about it, Osprey is the sort of company to publish such a book...
Only problem is that when they publish "Tomorrows War" in Spetember, a lot of gamers will then be using those rules to play 40k, as they are SO SO SO mauch better than the current 40k ruleset....