Well, you can't win them all; the anti-abortionist would have little to offer in such a case.
One thing that can be done in order to alleviate such cases, is to support and speed up the development of artificial womb technology. This would not only increase women's range of choice, it would also separate the medical need for embryos and fetuses from their current "method of production", i.e., women having abortions. This would spare a woman from having to get pregnant herself if she needed embryo/fetus tissue to save a loved one from a deadly neurological disease. Unfortunately, this artificial womb scenario is unlikely to appeal to an anti-abortionist, because it doesn't "save" any embryos or fetuses. On the other hand, artificial wombs would also reduce the number of cases of health problem pregnancies, including pregnancies where one must choose between the life of the woman and the life of the fetus. In other words, in this scenario artificial wombs can be used to save fetuses from destruction. Alternative solutions include cryopreservation and/or transplantation of the fetus to another womb.
Artificial womb technology and/or cryopreservation also opens up the possibility of producing, "farming" and harvesting embryos and fetuses in accordance to medical and clinical needs, just as one is now gearing up to produce (other) body parts and organs industrially. This will probably become an area of political conflict, since anti-abortionists are certain to oppose it.
However, the issue of using or producing embryos and fetuses in order to get regenerative nervous tissue may become irrelevant in a couple of years. Geron and other biotech research companies may be able to make embryonic research unnecessary and anachronistic by developing new knowledge about and techniques for neurological regeneration.
Probably some anti-abortionists will support the cryopreservation proposal, some will oppose it, and yet others - perhaps even a majority of them - will advocate cryopreservation as a mandatory replacement for plain abortion. The latter could create a good deal of social tension and conflict. Or perhaps this would simply divide and weaken the anti-abortionists. I suppose this too could be judged a successful result of the proposal by pro-choicers.