I think the heat sink issue has already been covered. But, in addition, the weight between a fiberglass (FRP) insert (stock) vs. an aluminum would be dramatic. I'm assuming you may be talking about astamped out version in aluminum, right? If so, then depending on the guage (thickness) of the aluminum, it may or may not be any lighter in weight. Also, the fabrication costs (tooling), finish work, and material would not be justified for the end result. Not saying that it an't be done. Just may not be worth the effort in the end. Going with a laminated process of fabrication either through fiberglass or carbon fiber would be the most economical for something that's simple in form.

Good luck to you if you decide to pursue your quest.