I'm not sure that Peter is self-aware enough to know his limits and I don't think he planned this in advance. Especially as it's a pretty crappy plan! If Peter knew about the horcruxes and therefore that Voldemort was likely to return he'd be in a better position to help him as a man, and a man of status in the community (see: Lucius Malfoy). If he didn't know about the horcruxes he'd believe Voldemort destroyed so there would be no end in view to life as a rat. As a man he'd be in no more danger from Death Eaters than any other Death Eater. He's used to leading a double life and I'm sure would be able to talk his way out of Death Eater suspicion. Plus he'd be protected by the Ministry.