I honestly doubt it'd do anything to overpopulation rates - it may even reverse the problem. If you could be certain of getting a child, even in the immediate aftermath of one partner's demise, even if you're female and well past the nominal child-bearing years, means that all the pressure that drives the thoughtful to reproduce before they're ready is gone. Bill and Melinda Gates make the case that the more control people have over their reproduction, the more reasonable family sizes are. Give them teachers, doctors and rubbers in Africa, and watch family sizes fall to western sizes - that's been the B&MG Foundation's experience. Put me in the not-worried camp.

Humanity not being ready for it, though? We as a species are remarkably good at rising to the occasion, in my opinion.

Well, if we could efficiently reduce the world population to about a billion and a half (perhaps a large-scale euthanasia program followed by freezing the bodies; that's some free carbon sequestration right there) we could live with our current level of resources without destroying the planet or shortage-induced political instability. That won't help with despot-induced-shortage-induced instability, however, so we must make sure that all despots and would-be despots die during the program. If you think that mind uploading is going to be feasible in the future, taking care to preserve the viability of the brains involved seems prudent; digital personas running in a simulated environment has the potential to be far more efficient than actually feeding and housing people.

None of this will help with militant fundamentalists - violent religious jihadis of any flavor, or militant nihilists like Aum Shinrikio - except to the extent that they're swept up in the purges, we'll still have to fight them with a reduced pool of people to recruit soldiers from.

And if you don't think that sort of program is a good idea, well, neither do I. But it seems like the choices are deliberate relinquishment - of either people, which is morally reprehensible, or of expensive but life-sustaining and per-capita-productivity boosting technologies like expensive medicine, fast transportation, and air conditioning (and with them, significant inhabited regions of the globe)… or more technology, instead of less. Though now that we know better, they're all likely to be much more efficient uses of non-renewable resources, and substitute renewable ones wherever feasible. The zeitgeist is going seriously green, and though nations at war have had access to weapons sufficient to scour their foes from the face of the Earth with the Light of God™, cooler heads have somehow prevailed. Every single time, since we discovered what horrible destruction we were capable of. We're still here to complain, and I consider that a fairly profound victory. We're still here, we're slowly stepping off the shores of our homeworld, We're deliberately trying to right the wrongs of the past, and that's gotta count for something.

Mhm, unsurprising indeed. Obviously unnecessary for procreation, but at the same time it could take a lot of the stress out of childbearing and remove the inequality some couples feel due to either infertility or same sexedness. I think it's a bad idea if a single individual does that sort of thing---then you'll wind up with not any different alleles or combinations of genes than the parent, and you may wind up with a large number of genes becoming homozygous recessive between both chromosomes---the same problem that happens when close relatives mate. Also, a single parent doing that is pretty damn close to the idea of human cloning, regardless of arguments for its similarity to parthenogenesis.

That said, again, I fully support the idea for any couple that chooses to do it.

Well, let's see - you referenced selfing as a potential problem. The problem's actually well-characterized, and low levels of it shouldn't have any chance of crippling the gene pool. Ah, and I see you mention parthenogenesis, which is the closest moral equivalent to this I can find. It has its problems, but since it persists in nature, it can't be that bad. Especially when most - really, the vast majority - of reproduction would involve two (or more?) parents.

Also, by the time selfing could carry out any real damage to the gene pool, I expect the Dark Lord of Derkholm scenario to have come about long ago. It's a wonderful fantasy book with peculiar sensibilities, a great concept, an intriguing world, and wonderful characters, but one of the background features is the wizard Derk and his wife have seven children who carry their bloodline (and, more critically, their germline). Five of them are gryphons, and two are human like their parents. (In addition to being a wizard of mediocre talent, I suspect Derk is a staggeringly talented molecular biologist.) Designer babies will be an event visible in the rearview mirror, receding over the horizon, with designer species in our recent chronological wake.

Yep.
Just another facet of the Freedom Of Form we'll be seeing in future as we unlock the capabilities of genetics. The form of a family will be freed too.