So for a Bleach story of mine that is absolutely dead, I was going to give Ichigo an entirely new Zanpakuto as opposed to Zangetsu. However, it would still follow the trend of his and Isshin's Zanpakutos naming convention: Shingetsu, which as far as I can tell is the correct Japanese term for a new moon.
It would come with its own activation phrase too.
"Plunge the world into absolute darkness: Shingetsu!"
Hoping to develop something of an idea (was playing the last of us).
So, basically. Ichigo never met Rukia, his house was actually protected by Isshin and Urahara, because here they are not irresponsible ex-captains that want to put the destiny of the reality on the hands of a teenager. So no hollow attack, Rukia goes around does her thing and leaves. Added to that given that Ywach can see the future, he doesn't want the only person who could kill him to awaken his powers, the quincy king even cares in his own way for Ichigo.
So Ichigo doesn't awaken his powers and events conspire to prevent him becoming a Shinigami. Shit still goes down, Orihime dies by Sora's hand, Chad dies with killer hollow, Tatsuki and friends die on the fake Karakura arc, the city is almost nuked by Aizen, Aizen kills Yamamoto but is prevented from creating the king's key by either Urahara or Isshin.
Ginjo happens on the backyard and then we have the Ywach, thing, he ascends, kills everyone and start destroying everything, here should the story begin. While Isshin and all the other people manage to stop Ywach by some convulted plan, maybe with Uryu arrow or something, Ywach almost destroyed everything, and that includes the mortal world. The Earth was send decades to the past, with earthquakes, disasters, etc... The result is a semi post apocalyptic world with hundred of thousands dying, not receiving Konso and becoming Hollows, years of famine and sickness with very few Shinigami, almost no Quincy and ravenous monsters almost every one kind of knows are there but very few can see.
Years after we have a lot of Fullbrings, a world that kind of is trying to rebuild itself and then we have Old man Ichigo, rugged badass with strange powers that he devolped to try and protect his sisters and the very few people he actually care about, probably the most powerful Fullbring, with some others skills (quincy things) roaming the world trying hard to survive after having to send his sisters to the after life (tentative if he can actually do Konso or not, for extra edginess maybe Yuzu and Karin ended becoming a Hollow) with a Yandere arrancar Orihime following him around. While the soul society on the brink of being destroyed is trying to rise up, because Ywach wasn't as dead as people wanted.
So those would be the basics, kind of playing around with a hogyoku reincarnated as a human girl that humans find can destroy the monsters with her mere presence, with Ichigo forced to take care of her, Aizen maybe reincarnating between the years, too powerful to actually die, the realities barely existing by a thread, with Urahara wanting to use Ichigo as the next king only to find a possible remplace in the Hogyoku girl and the Oldman Ichigo trying to protect the girl, discovering his father was alive and never went to help him or his sisters.
I like the idea of badass Old Man Ichigo. It's a neat idea, especially the Fullbrings being more prominent. I can see Seireitei watching and waiting to see if they need to pull another purge, just in case. Or perhaps they'r e caught off-guard, when they finally manage to open a gate to a more populated area with powered people. I'd love to see this written out.