Could Time-Turner be used to save Black?

[kneazle255]

No: HPFGUIDX 82334

Calimora:
For me this is the most telling evidence. JKR has stated that the 
dead stay dead. James and Lily are dead and aren't coming back. 
Sirius is dead and isn't comming back.... Assuming that he died in 
the first place.

Kneazle responds:

I agree with you totally. I don't think he's coming back. 

But--this is an errant thought--there are lot of magics in the WW 
that we know nothing about, including that room where people can be 
aged or made younger at will that facinated Ginny so much.

Sirius had a pretty miserable life. Hogwarts was apparently his high 
point by far.

That room, a bit of time travel...hmmm. I wonder if somehow or 
another he will get the chance to do it again?

A young sirius with no knowledge of his previous life aged 11 returns 
to Hogwarts for another crack at a happy Voldemort-free life. Let's 
make Harry his godfather!

I am a sucker for a happy ending.