quotes from another article on human animal chimeras and possibility for unlimited compatible organs avaialble for transplantation

-By modifying genes, scientists can now easily change the DNA in pig or sheep embryos so that they are genetically incapable of forming a specific tissue. Then, by adding stem cells from a person, they hope the human cells will take over the job of forming the missing organ, which could then be harvested from the animal for use in a transplant operation....

 “We can make an animal without a heart. We have engineered pigs that lack skeletal muscles and blood vessels,” says Daniel Garry, a cardiologist who leads a chimera project at the University of Minnesota...

One reason is that if his iPS cells develop inside an animal, the resulting tissue will actually be his, a kind of perfectly matched replacement part. Desperately ill people on organ waiting lists might someday order a chimera and wait less than a year for their own custom organ to be ready. “I really don’t see much risk to society,” he says..-source technologyreview

Interesting snippet from another article on human animal chimera research.   A possible near term solution to the problem of organ transplants. 

Very very interesting things could be done with chimeras, I see a lot of potential.   You can eventually not only design these to be compatible with humans but you can use these to research the function and effects of genetically modified superorgans.    Given that rat mouse organ chimeras have already taken place, it would be interesting to see if replacing one of a few organs with the longer lived version organs have any significant effect on lifespan. 

Another possibility is that if the mother animals are suitably modified they might even be able to function as living artificial wombs.    Accelerating the arrival of artificial womb technologies.  Artificial wombs would when combined with a few other techs allow for same sex couples to have children irregardless of their biological sex and it would also help enable single individuals to reproduce, and would free women from having to carry the delicate baby around for 9 months everywhere they go.

Dna Hybrids and Chimeras, high speed possible solution to organ transplant needs.

 "But by the end of the year, eGenesis -- another company eyeing pigs for xenotransplantation and founded by the infamous engineered-biology scientist George Church -- announced it had successfully modified 62 genes in pig embryos using CRISPR tools. Progress happens at light speed in this field.

Overnight advances in gene editing have had other effects. The NIH recently announced it will lift a moratorium on providing federal funding for research involving humanized animal embryos, which many expect to result in an explosion of research."-source link

 While genetically altering animal cells to be more compatible with humans is promising, the idea of humanizing embryos, especially if it involves using chimera research, aka mixing human and animal cells is even more promising imho.  You would most likely need to deal with the immune system, perhaps focusing genetic modification on the basis of cellular immunity to generate tolerance without compromising immune function. 

Already single cells have successfully been transplanted between species and lived as long as the new host.   And human animal chimera research is still undergoing

"They believe the animals, which if they had been carried to term would have developed a human internal organ, but would have looked and behaved like any other pig. The goal is that in the future, similar animals could potentially act as a ready source of organs for life-saving transplants.

To create the “chimeric” embryos, the scientists used a gene-editing technique known as Crispr to knock out a section of the pig’s DNA necessary for the embryo to develop a pancreas. 

Human induced pluripotent (iPS) stem cells were then injected into the pig embryo. These are cells that have the potential to develop into any tissue type in the resulting foetus. Although genetically foreign, they are not rejected by the pig embryo because its immune system has not yet developed."-source guardian

3d printing is probaby many many years probably decades away, human cloning is a no go, as even if you could develop brainless human clones the idea might be repulsive to most.   But seeing as animal suffering goes unnoticed at large, at least taking the lives of these animals can eventually be used to save lives rather than just providing pleasurable rack of ribs.  Hypothetically you could take stem cells from a patient, and transplant them into a suitably modified animal embryo, creating a custom made chimera with the specific organ or organs that the patient needs.   Being genetically identical to the patient there should be no need for immune suspression nor chance of rejection.   

While the article makes comments on possible pig brains being compromised by human stem cells, this can be avoided by the fact that not all genes expressed in the brain are expressed in every single organ.   If genes exclusively expressed by central nervous system cells but not by the desired organs are genetically knocked out, then no viable neural tissue can develop even if the stem cells contaminate the pig's central nervous system.  Organs that have some small amount of regulatory neural tissue, might or might not be too severely affected, and if they were viable solutions are likely possible.

As to vascular tissue, it could be made fully human, but we'd have to see what level of humanization is possible before complications arise with the mother animal's immune system, issues that might be resolved by interfering with such immune system.   Hypothetically so long as human neurons are not being created in the brain, the chimera can have the rest of the body human, assuming immune issues and other compatibility issues are taken care off, there'd be no ethical problems.  No ethical problems besides the killing of animals to harvest tissues, but that's no different than the ethical problem of killing animals to harvest their meat, an ethical problem to which many do not seem too concern themselves too much about.