Let's just play devil's advocate and say that the Pope is a senile old drooler, utterly incapable of doing anything for himself, and dying in complete misery. It's still a sin to pray for this man's death, and it reveals that you think that some people are inherently less human than others. Where do you draw the line? The senile? The handicapped? The unborn? This line of logic is the slippery slope that can only lead to eugenics.
How about praying for God's will instead?
BTW, I agree with what you said.