And why exactly would we want to do this? What if the dead do not want to come back? Are we to force them? Or perhaps you are suggesting, and I think you are, that they would have no choice in the matter. With spacetime engineering they would “never even have died in the first place” so its not really “bringing them back” now is it? And, If they were only simulations to begin with, who cares what they “want” anyway. They never really had free will or a will to begin with, they only had the illusion of one so why start worrying about what they may or may not want now. They are too dull to know that it’s all just a big fake out run by the Engineers and who are we to spoil their ignorance by letting them in on the game. They will just be happy to be alive again. Won’t they? Who cares, I’ll be happy to have them alive again so it’s definitely worth it. Isn’t it?