First off you'll need to use an image hosting site to link to (I followed your links by quote then copy paste, most people wont bother).
The actual concept looks pretty sound, you'll need to shorten the chest plates lift the ab and then lift the girth belt and ammo belt as they should be at the waist not the hips.
Best advice I have is to just start building - you may find an awesome fabric or leather in some colour and decide to use that. Took my a couple of years to finalise my design after a few repaints, some people try even more, some have a scheme set before they start - just take how long it takes you to be happy with it.
The helmet should extend past the chin just a little, enough that you can't see the chin from the sides when it's worn neutrally, but not long enough that it's extending further as it will start clipping the plates when you move.
If you plan to fibreglass, resin and bondo the traditional way (resin & glass inside then bondo outside leaving the paper between them having soaked in resin), do take into account that you cannot do that on duct tape.
I actually do this on purpose by layering the inside of my helmets with duct tape and resin & glass'ing onto that. Then remove the paper and duct tape and bondo straight onto the fibreglass.
