Some good ideas there. I'm going to try to spray some extra Terminator and Halo pieces in flat black. I think they may fit in nicely with the overall aesthetic. I really like how the reversed chest piece looks.
Funny you should mention Terminator.
B&W Hunchback and Dracula heads, and GitD Creature parts. Couple of Terminator and Cylon parts in there and a War Machine Chest. I agree, Halo seems like it would be an excellent fit.
And, last one:
Head swap between the old and new Borg mates, b&w Mummy with War Machine hand and foot, and a Maximum Zombies head.
Lots of possibilities. I wonder how hard that first Borg is to come by these days...