Given the recently revealed survival of a certain someone, I've been thinking lately about the other big, shocking death of recent times. What if Oda wanted to revive Yasuie? I'm sure all these points have been made before, but given their current relevance, I thought I'd lay them out again.
To be clear, I don't want this to happen. I think his death was a powerful moment best left alone. But if Oda did go for it, he's already laid out enough seeds to answer the key questions.
Why didn't he die when he was gunned down?
After being injured, Toko rubbed Usopp's toad oil on his wounds. Usopp said his medicines would seal any injury, and we all know how things tend to go with Usopp's lies.
How did not one notice he was still alive?
Yasuie's death has been confirmed by only two people so far. Toko and Kanjuro. Toko was a distressed child. Kanjuro is a liar, and it's worth noting that it was him specifically who took the body away to lay it to rest. He did this alone, as far as anyone can tell. The only other person who has been shown in close proximity with the corpse is Franky, although the dialogue when Kanjuro takes it away for the burial does imply the people of Ebisu might have watched over it for a while. These are the main holes in the story, but I can see Franky not getting a chance to check vitals while fleeing the battlefield, and the Ebisu locals keeping a respectful enough distance to not notice him being barely alive. And even if the actual act of burying Yasuie was watched, he was completely wrapped up in a sheet when Kanjuro carried him off. There would have been ample opportunity while travelling to spirit away a barely-alive Yasuie and fill the sheets with something or someone else to bury.
Why would Kanjuro keep Yasuie alive?
The motive is Yasuie's distinct blue, hedgehog-spike hair. Kanjuro has a specifically emphasised habit of taking real human hair for his brushes. There would be prestige in having a brush made from such distinct hair from such an important person, and a particular catharsis in it for Kanjuro, given how Yasuie was such a big Kozuki supporter. This will be the really interesting clue to look out for, either in the colour art or the anime, whichever gets there first; do the bristles of Kanjuro's brush take on a new colour on the day of the battle (although he could just as easily be saving the Yasuei brush for a special purpose.)
I don't truly expect to see Yasuie again at this point, but I really won't be shocked if it happens, and given Oda's history with this kind of thing, neither should anyone else. The only truly safe deaths are Ace, Whitebeard and mentors in flashbacks. Approach anything else with caution.
Edit: used the wrong little girl's name