[1] “none” (dead, inanimate object)
[2] “potential” (babies; part of their nature), (coma patient, knocked unconscious, mentally handicapped – those that have shown to be able to engage in argumentation, at least once, and may be able to do so once again)
[3] “always” (children, adults etc.)

So therefore; [1] No Rights, [2] “Guardianship” or “Trustee” Rights, [3] Full self-ownership.

This is thus both logically rigorous and accurate.

Both gentlemen make it clear that they are fully aware that a fetus is in significant ways not an adult – e.g. it cannot consent or intend and thus not enter into any form of contract. But they cannot resist the game of trying to make it fit somehow, such as by drawing analogy with a co-operative trespasser departing as fast as they reasonably can, (or conversely an obstinate trespasser declining to leave within a reasonable time).

Perhaps the way ahead is to recognise that young humans – whether at the stage of fetus, baby, toddler, or child below the age of reason – belong in a different category, neither adult nor thing (that can be possessed by an adult). The challenge for libertarian thought is to become 3-dimensional enough to encompass such a category; to add an axiom that fits alongside its existing axioms.