Well, its possible...but I think as soon as you started it the carbongraphite block would get a lot of cracks and eventually just shatter. It would be cool looking, it could be a "show" engine.
This company makes the composite piston/sleeve combo. It looks as though they have come out with a new copper based P/S as well now. I haven't looked at thier site in about 6 months...
http://www.k h b r a c i n g.com/AG_Piston_Sleeve.htm