Well, sounds like you already have tons of good ideas... but here's what I did, just in case you find it helpful. ^^
First I used some wire mesh for a base, being sure to fold in all sharp edges. (sharp wire stab in the face=bad). Then I used Ridgid Wrap, the plaster coated gauze stuff, to cover the outside bit. Then, on top of that, I smoothed on a layer of Paperclay, which can be sanded pretty nicely. Then paint. I used lenses from a pair of sunglasses for the eyes. Also I applied some felt on the inside, so it wouldn't hurt my face. I attached a small wool hat to the top, so it would stay on. All in all, it wasn't heavy, and it was pretty sturdy, even when I dropped it. A couple of times. ^^;;;
Hope that helps... if I didn't make any sense, or if you have questions, feel free to PM me.