I don't think that existence is subjective, so universal preference either exists or it doesn't. It has been a long time since I've sat in a philosophy class though, so I'd welcome a correction.
So if I were to tell you that I really did prefer to be a slave you would say I am not human? You are excluding as 'human' any individual who are not capable of understanding the concept of 'ownership'. Do you seriously believe that babies and the severely mentally handicapped are not human?
If you are operating with such a divergent notion of 'human' (and thus 'morality', 'universal' and 'preference') then there is no point in having any further discussion with you or considering anything you have to say.
You won't end up with any single seed values you can match any given instance against, but with multidimensional matrices that represents multidimensional scales.