Basically this is convalescent plasma therapy, but taken from a deceased person, which is actually quite feasible:
Contrary to what you might think, blood from cadavers is not only usable, but quite safe. "For six to eight hours, the blood inside a dead body remains sterile and the red blood cells retain their oxygen-carrying capabilities," Mary Roach reported in her book Stiff.Jul 22, 2015
Basically this is convalescent plasma therapy, but taken from a deceased person, which is actually quite feasible:
https://www.realclearscience.com/blog/2015/07/a_simple_solution_to_end_blood_shortages.html