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3d printing or laser cutting also comes to mind.

I do not know if sintered brass is strong enough (Laser sintered fast protoyping)

And laser cutting is not what you think. (damn, I am not thinking of an easy way to explain it, so I will just give up. A laser melts brass, not burn. Other metals that can be cut you use a gas that will react with the heat and oxidize the element.)

That's interesting. I figure this might be a cool problem for someone to crack. :) I'd really like to see an oval shaped tap hole some day.