I think they should extend it to about age 20. As long as they are going to use an arbitrary age range anyway, might as well make it long enough to be useful.
I support abortion because nobody should be able to tell a woman what she can or can't do with her body. If she doesn't want to bear a child, she should be able to stop the pregnancy. But once the child is born, that issue is over. And yes, as discussed in the article, it can be traumatic to give a child up for abortion, it can also be traumatic to be in a serious car wreck, get ebola, have your house repossessed, survive a big hurricane and/or be raised catholic. But none of those are under consideration as reasons to not do something.
If someone wants to argue that we should consider euthanizing children born with severe and crippling birth defects, that is a separate issue from abortion. And since this paper argues that it should also be fine to "post-birth abort" healthy children if nobody feels like dealing with them, then the proposal oversteps a line that normally only mass murderers get to cross.
When I support abortion, I am supporting the living person over the fetus. If there were a way to remove the fetus at that point and put it in an artificial womb and allow it to develop and continue existing until can live on its own, I'd be all for it. But if I am going to support the living person in the case of abortion, then I also have to support the living persons in this instance, and I cannot condone "aborting" or otherwise doing in a child after he or she has come in to the world. I, for one, refuse to label a newborn as less than alive or otherwise less worthy than a 10 or 20 or 30 year old.