The Elder Wand And The Time Turner

"Nothing can be changed because anything a traveler does merely produces the circumstances they had noted before travelling." Reads Novikov's self-consistency principle in regards to time travel but what happens when someone does take note of inconsistencies around the death of Severus Snape and is compelled to do something about it? Parings: Severus/OC, Ron/Heromie & Harry/Ginny