All of the inorganic systems mentioned already are available now to the home user, look up Shapeways or Moddler for bureau services, printed straight into metal – no problem sir, bronze perhaps?
In the bespoke jewellery business which is where I live it is not uncommon to design a piece on cad, have the customer approve the model, bang the file off to a bureau and cast straight from the returned plastic model.
I have a home type 3d printer on order and fully intend to use it that way and I'll be very suprised if it doesn't make a few bits for my models as well.
Andy