well, you're not going to be able to get the detail out of your armor like you would like. it's very very hard to work with, and the end result would LOOK the same if you were a master craftsman. In most cases, plastic will look better because of it's ease of working.
I don't want to discourage you, but that may be a little too ambitious. There's a reason they use plastic in movies and theater props. Its mostly because it looks better, and is cheaper.
We've had this discussion here many times, it seems like every 2 or 3
months. Theres really no good reason to make your armor in metal.
You're going to start out at a serious disadvantage to others who aren't as
limited by their choice of material. It's just going to cost you so much
more, slow your progress down seriously, and just end up looking like
every other fiberglass or ABS suit out there once it's painted.
I mean if you absolutley feel you want to be the trendsetter, go ahead,
but you are doing something no one else here has done... so unless you
have serious experience in fabricating and TIG welding aluminum
already... I don't know how much we are going to be able to help you.
I think its a preference issue really. If you want heavy and strong, use
fiberglass reinforced resin cast in rubber molds. If you want lightweight
for mobility, use fabricated or vacuumformed polystyrene.. which can still
be reinforced with resin afterward....