from the stories I have seen it is adult stem cells that have been beneficial not the embryonic ones.
Then again, I think one day scientists will be able to produce a proto-cell, sort of a blank that can become literally anything.
Any cell can become anything already. They are a blank, at first. What they turn into is determined, as far as I can tell, by the mitochondria. They are like the platoon leaders of the cellular world.
If we could 'reprogram' the mitochondria at will, then the problem would perhaps be solved.