this will be my RAW for creating difrent space marines and special charackters, its still a work in progress but u get the general idea, i had allot of problems modeling the hand since i couldnt get a good reference picture for the palm of the hand of the power armor, so i had to improvise, also, i edited the shoulders a bid wider from the neck for when i'm going to animate, cuz i just know those shoulder pads are gonna get in the way.
next is the backpack, then shoulder pads and helmet

done in 3ds max

edit: oh and i know the lower arm and hand is to big in this picture, its already been adjusted, i'll update this pic soon

Edit2: ok so all thats missing atm is the helmet or face and some minor adjustments