That blood would be given an element of acquired sacredness for it came from a person who already died
No it wouldn't.
Blood has no sacredness unless it represents the life of a creature that has been taken. In that case it could be presented on the altar or poured out on the ground. In both cases it symbolised returning the life to the life-giver.
If a creature died of natural causes its blood had no power or significance.
If a creature is still alive its blood has no power or significance.