Hm, well, I think the most obvious one would be he had a vile of anti-venom and blood replenishing potion somewhere on his person that he managed to get to right as Harry was turning away. But, he couldn't just get up and walk away after that, even if he did manage to stay conscious. So, after the final battle, Harry sent Madam Pomfrey to the Shrieking Shack. She managed to get him stable enough to move, and then brought him to the infirmary, where she fixed him up.
Ms_Figg writes really good stories, I enjoy 阅读 her stuff. That's a very interesting idea she wrote (that 你 quote).
I could not tell which are best 或者 most outlandish, as they are all good to me in that sense that everything that makes him alive in the end, is indeed a great thing. Even the classical potion mixtures + bezoar are fine 由 me. Anything, as long as he lives.
Besides, he's a clever man. Fore-warned is fore-armed, as they say. (See Protowilson art herebelow.)
In one of my already 发布 fanfics, I used the healing power of his 爱情 interest to save him. Blood and sacrifice, again.
In another fanfic I'm 写作 (not 发布 yet), it's just the very basic potions + bezoar stuff that helped. Plus the quick action and loving care of his 爱情 interest. Oh, I forgot to tell : Fawkes helped him with his tears. 你 know, phoenixes are helpful to those that had remained faithful to their masters. So was Severus. So Fawkes came to his rescue.
(Yes, I write Severus/OFC pairings only.)
I'd like to read other ideas though. I'm sure there are very good ones out there. 50 ways to make Severus Snape to survive : that could be a nice compilation !
Albus Potter and Scorpio Malfoy go back in time, and instead of trying to save Cedric, go to the Battle of Hogwarts, stupefy the trio, get Albus Potter to impersonate Harry, gives Snape anti venom, blood replenishing potion, dittany, etc. He then collects Snape's memories, leaves the memories in Harry's hands with a note saying "From Snape must watch asap", reenevates the trio and then quickly goes back to the future with Snape.