Since my original post on this I have spent a fair amount of time doing some research and amassing parts and ideas which have begun to find there way into my initial test model (shaping up to be Tanith scout Bonin) seen below.
As I wanted to keep my guardsmen to a realistic scale and proportions I've used Elysian guardsmen legs (from Forgeworld) as a base and sculpted the torso, neck and arms on top since there is a lack of pieces in the GW and Forgeworld ranges that fit with the look I'm going for for these. I have also removed the kneepads, thigh padding and harness straps from the legs and replaced them with a look more fitting with the Adrian Smith artwork I am using for inspiration.
There are still a lot of details to add, and this is obviously still very WIP, but I figured I would share it since I feel it is a sizeable step forward in the progress. Incase you are wondering about the pose - he's going to be moving silently to the edge of the wall he has his back to, weapon raised in his left arm ready to break cover and bring down the enemies of the Imperium.
More soon! Feel free to let me know what you think in the comments section.