I have thought much about this as regards my devout JW wife. If I did it against her wishes she would never forgive me. Therefore I have decided that if it ever arises, I am going to let her JW family make the decision, informing them that I am against it.
I know the decision they will make, and if she lives I think everything will be all right. But if it happens that she dies, and then later the stand on blood is done away with, you can be sure I would not let them forget it.
I think the blood thing is being subtly dismantled anyway so I don't expect to ever have to face it.