I wonder how you could possibly see 'value' in seperation from the character traits that you see as secondary? That's not a dig btw, its a genuine question, because your only example was that of newborns. If you were going to use it in, for instance the example you used, a legal setting how could you possibly seperate secondary value from primary value?
It is a weak measurement, where the main use is to establish who is to have fundamental "rights" as a person to begin with. Continuing the example of newborns, once established that they have no value as a person, it follows that they have no rights as a person. (though I'd say that, once grown up to the level of having gained value as a person, they gain the right not only not to have inflicted, but also not to have been inflicted, any treatment deemed abusive) Thus, there is no reason to disallow post-birth abortions for up to a couple of months after birth. Similarly, people whose "person" has ceased to exist (ie. through extensive enough brain damage) lose all of their rights as a person as soon as this is clearly established.
The primary "valuing" excludes those having no value according to it from having any value according to the secondary. Apart from that, it typically becomes as good as irrelevant once the secondary is taken into account.
I might just as well adress in short what comes secondary to me as well. First of all comes harmlessness, ie. that the person does not constitute an immediate danger. Then comes usefulness, which is quite a broad area, along with, which to some extent is needed for the first requirement as well as for the second, reliability. Most things I value according to can be said to be a part of these, though the prioritization varies greatly.
If a person is harmless, but neither have any positive nor negative impact, the value from the primary judgement, which is basically that which is needed for a person to be respected as an individual, remains unmodified. Most people have a value ranging from near-zero to "somewhat detrimental", quite many being more so. A pretty large amount of people have a slight positive value, a smaller portion having one more significant.