After a lot of tinkering with a Minifig Piraka body I managed to come up with this. I decided that, on the grounds that the Geth is a race of its own, they would have their own cultures, traditions, festivals, leaders etc... on their own planets. This is not one that fights. The job of this Geth is to single out new Geth to be fitted out for battle in their holy crusade.
*Extends a claw towards the crowd, silver discs glinting in the alien blue light emanating from its nanite scepter, calling forth new citizens to further their holy battle against the heathen*
This is a shot of the back.
This is how I constructed the head. It's a Piraka Minifig head rotated 90 degrees and attached by the tail hole to the torso. A trans-blue stud covers the neck hole with 3 helmet visors Blu-Taked over the face (Okay it's white, but you get the picture). I have the peices to make a red warrior one, which you actually encounter in the game, when I get around to it.
Feel free to make your own Geth Minifigs if you have piraka heads. I only borrowed mine off my friend, and don't actually have any to call my own, so i'm a bit strapped for parts.