We should really just grow clones in labs and harvest them for parts.
Remove the brains at week 16 through genetic and surgical means. Keep the rest of the body artificially alive. Expensive upfront, but massively scaleable.
MHC, ABO, etc. complexes engineered to be transplant compatible.
We could replace organs and blood as we age. In fifty years, full head transplants could tackle every disease except brain and blood cancers and neurodegeneration. Every other disease solved.
It's so simple and obvious, but nobody can get over the egocentric morality qualms and superstitious ick factor.
Our bodies are plants. It's our minds that are special. We should be able to transplant every other part.