I like the way you answer the canon-compliance question. It's very level-headed and fair. And the many reasons a Potions Master might appreciate a handy-dandy Phoenix are spot-on. I always expected Fawkes to make a re-appearance at Snape's side, and the dangling thread left by Fawkes simply flying away after Dumbledore's funeral seems like a missed opportunity to me. But then, if I started counting the missed chances and unfinished character arcs in the books, I'd totally derail myself into a rant and I need to concentrate on finishing my fic. ;)
I'd like to see more of Harry rescuing Snape, who by this point really seems to need it more.
One of my favorite Snarry images ever is ponderosa121's Snarry Games submission, What Shapes Us. It's such a visceral depiction of Snape submitting to Harry, of Snape needing to be rescued, and there are so many clues to ponder - the Dark Mark on Harry's arm, for one - that it pushes all sorts of buttons for me. So yeah, I agree, Harry rescuing Snape would be a really interesting turnaround and a way to explore both the vulnerability revealed by the Prince's Tale and Harry's newfound maturity. It takes a different kind of heroism, after all, to rescue your lifelong enemy, and it's something Harry clearly doesn't have in canon.