The plan is to pour a thin layer of urethane resin with microballoons for filler to pick up all of the surface details. Then lay over the resin with fiberglass mat and cloth. Then layer over the fiberglass with urethane foam. Once I've got that figured out, I'll make sets with a first layer of clear resin with black tinting and aluminum powder for a convincing metallic surface.
The material cost isn't really the issue (I'm buying resin in 10-gallon kits lately), instead I'm worried about making the whole thing lightweight. The first casting of the chest plate alone is about 12 pounds. At that rate I'd be building a suit that would weigh in at around 80 lbs. It's very strong, but unless it's bulletproof it's not worth carrying all that plastic around.