The one confounding aspect is whether - and to what degree - an unvaccinated person can get the spike protein from a vaccinated person via "shedding", (through bodily fluids etc) without having had a jab themselves. It may be that not all unvaccinated blood would be as "good" as hoped. But that's for another day I guess, a separate unvaxxed blood supply would at least be a start. I don't think they will agree to it though, for fear of implicitly admitting there MAY be a problem with (some) vaccinated donors