I have been researching this topic recently because of my father-in-law. He has started to tell one of the elders off that the Society has really screwed up the blood doctrine.
In my research, I've learned that:
-The Society admits that when the bible mentions blood, it is only in connection with taking it in as food.
-The Society has also admitted that blood transfusions are tissue transplants.
-Then the Society has admitted that they cannot be the judge of anyone who accepts a tissue transplant.
The only two things I see that hold the Society back from permitting blood transfusions completely, without disfellowshipping, are:
-They are still very adamant about teaching that blood transfusions are a nutrient (by using false analogies) and therefore should be rejected. (This is completely untrue, proven by modern medical knowledge, hence why they quote 17th century medical science when it comes to this.)
-That it is a violation of God's law if someone sustains their life off of blood. (This is something that is NOT taught in the bible. It is a completely man-made rule.)