I think the first concern is still a bit farfetched. Are judges really going to think, "I could sentence this man to death, or to life, but since we have a cornea shortage right now, I think he should die"?
And yeah, the second objection is completely idiotic. Firstly, what's wrong with the idea of letting condemned criminals have a bit of redemption through their deaths? Secondly, if someone's waiting for a heart transplant, I don't think they'd care very much about whether the heart belonged to a death row criminal. I mean, if you're really unsure about this point, tell the patient about it first, and let them decide if they want it.