Isn't the "blood components are still blood, thus a JW wouldn't accept them" essentially the same argument that JWs reject when discussing the trinity?
I.e., "The Father is God, the Son is God, the Holy Spirit is God, and yet there are not 3 Gods but only 1 God"...isn't that pretty much the same as "Red blood cells are blood, white blood cells are blood, platelets are blood, plasma is blood, yet there is just one 'life-giving substance' named blood"?
If a JW asks you "If Jesus was God, who was he praying to?", couldn't you counter with "If plasma is blood, why can't you accept platelets?"
Make sense? Reasonable?
Or is my brain starting its weekend early?