I love "What if" stories and this one is perfect! The different scenarios that played out and in the end the only one that really made the defeat of Voldemort possible is exactly the one Severus has lived. His observations about his younger self and all the others were a delight to read. And a lovely happy end for the real hero!
Now I wish to read a longer version of the one where Snape is Harry's godfather, but with a happier end, like Harry surviving and growing up with Snape ... Wonderful story!