well hey, if this guy's gonna have a bolt pistol, where one bolt is harder to make than a whole lasgun, then a chainsword/axe is no big deal. I said gasmask because almost all of the cultist models i've seen have gas masks on.
I was thinking the belts over, under, and through the plating, to hold the armor on and make the costume more complex.
"You all did see that on the Lupercal
I thrice presented him a kingly crown,
Which he did thrice refuse: was this ambition?
Yet Brutus says he was ambitious;
And, sure, he is an honorable man."