So the book has many effects that are reliant upon your devotion to a God. What if one were to stay unaligned, as I plan to with my Alpha Legionnaire? For instance, the mutations... many of them have effects that are God-based.
My Legionnaire's goal is to gain enough infamy before hitting the 100 corruption threshold to lead a Black Crusade as an un-ascended Champion. Basically, he's going old-school Alpha Legionnaire via Dan Abnett's Legion, bring down the Imperium to starve Chaos.
I'm going to avoid aligning myself with any one God.