Cool idea
For wiring, I would do as suggested above. Set up a jig to pre-bend the wire into the shape/size needed for the mold. Insert the wire, then pour the fiberglass in. You can make the jig by hammering 10 penny nails into scrap wood and bend around these. While most of us are using the 308 or 316, you might try string wire like you would use for a spinnerbait. Yeah, a real pain to bend, but it would hold its shape better. I think you'll find that is what is used in commercial plugs with molded in thru-wire.
Jigman