I agree that vanity is a bad reason to clone. But people have children all the time with similar kinds of rationales, but we don't forbid it.
I'm not so sure about the replacement parts issue. If a couple has a second child to give a bone marrow transplant to a first child that is sick; as long as they love and care for the second child in a similar manner to the first child, I don't think there is a huge problem in doing that.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13