Funny... one of my early considerations for an art installation for '11 involved paper mache` human figures. Here's what I've found...
Mannequins are a great form for paper mache`. You'll need some kind of release agent, one that doesn't retard the drying of the paper mixture. My plan was to coat the entire body and when dry, cut a seam all the way around, on the outer edge, pry off the paper, remove the mannequin, then re-assemble the two halves and glue them together with a new layer of paper.
Paper mache` is strong enough to hold the mirrors. Just do it right, do it thick, do it carefully.
My current experiment is still in progress, but so far has yielded excellent results: egg cartons.
Get the egg cartons that look like they're made of paper pulp - 'cause they are - tear them up into small pieces, combine with hot water and some white flour, and stir until the mixture is dissolved into a thick glop. Spread this over a frame of hardware cloth.
What you'll get when it dries is a near rock-hard structure. I've left my test piece outside for two months, now... it's endured heat waves, rain, and now snow, and is still sturdy, inflexible, and in the same shape in which I left it. It's turned a little brown from the exposure, but then, I didn't put any finish on it, duh.