Tilting his head, the Dark Lord pondered, "Wormtail might have been a snivelling coward, but he was always good with this. In fights, he hid like the rat he was, but when it came to ritual magic, he was extraordinarily skilled. Yes, I believe the ritual would have worked, but - as you have so helpfully pointed out - we lack key ingredients. I need to find another way to gain a body."