OK so now i've warmed up a bit, I'm going for a REALLY big, death-defying streatch here:
Voldy told Lily to stand aside (this has always worried me; i mean, why?) Maybe Voldy intended to just kill Harry but he needed Lily for something. We don't know how voldy does a Horcrux. Maybe he needs the victim to say something; somehow be involved in the creation of the Horcrux before or as he's killing them... ???? So maybe he just killed James, expected to kill harry (which was his main aim) but then intended to kill Lily and make a Horcrux in her wand...???? We are told that Lily's wand will be important AND that Voldemort liked to take souviners. MaYBe the two are tied????

Stretch, stretch. Don't forget to breath!!