I really like approval among single-winner methods. It’s a clear improvement over plurality and encourages honest over strategic voting with 3+ candidates. Promoting candidate diversity without punishing voters for supporting them is the best way to help minor third parties become relevant.
Among ranked voting methods, I prefer Condorcet methods over others.
Instant runoff voting / single transferrable vote has some merit in the multi-winner proportional representation case, but isn’t fit for purpose as a single-winner method.
I think FDA rules explicitly prohibit paying blood donors in the US. Ostensibly because if you do, the donation centers fill up with junkies who’ll lie about not having hepatitis so they can get paid, or steal IDs so they can go twice a week until they die of anemia, raising the costs of safety testing and generally being injurious to public health. Of course, everyone else involved in the process gets paid, just not the donors – quite dearly, as you’ll learn if you’re ever on the receiving end of a transfusion.
Plasma is paid because it falls under a different regulation and their research and industrial customers don’t care that the plasma came from a crack whore.