I think the difference is that when Rowling writes that Voldemort took steps to insure that he wouldn't die, I take that to mean that he couldn't die of old age or illness or a dagger through the heart, muggle-type ways of dying if you will. I never read anything about trying to resist the killing-curse into it.
Looking at it that way, my idea of someone dying for him could possibly work. However, if you imagine that she means he was seeking for a way to counter
Avada Kedavra, as I'm guessing you have, then no, my idea doesn't hold.
It's all in the way you interpret what is said. Like when Hagrid tells Harry that there wasn't a wizard went bad that wasn't in Slytherin. Many people took this to mean that Sirius (who everyone thought went bad) and Wormtail (who actually did) must have been in Slytherin, and that therefore James Potter was as well. I merely thought that Hagrid was exagerating, as people are wont to do.
As to Voldemort not dying because he took steps to insure he wouldn't being or not being enough, I was merely trying to coax out some ideas as to
what kind of steps he may have taken.
Sum sui generis
Vs