The fact that the fetus can have the status of a rodef at all implies that it does have an aspect of personhood
Interesting theory and not implausible. I would expect there to be a source in Rishonim or Achronim as such (Rodef = person), and invite the Olam to help out with finding such a source. It would be difficult though. The closest that I can think of off the top of my head is a Shor Rodef.