Hi, Sionna! My version doesn't negate the bargain Voldemort already made with Severus. It's in addition to it, not instead of it. I just think there is no way on earth Lily would step aside (thus triggering the original bargain) unless she got some kind of assurance about Harry's life from Voldemort. Yes, he'd be lying, and so would she. But doesn't this seem more believable than what we got? Or can you believe, as a mom, that any mother would let this monster get a clear shot at her child?

The original scene just makes Lily look like a panicked girl - not a particularly clever or powerful witch. I end up admiring Narcissa Malfoy more than her. Seriously!

I'd love to see your complete reasoning about Severus and his reasons for joining the DEs. Of course, I think you're right! But, again, Rowling was working to diminish his character, and ended up diminishing her story as a result.