Note: Skip to the end for a shorter version.
Unlike most in the thread, I actually enjoyed and vaguely followed Bleach and I can tell you that fixing the ending of it is fundamentally a bad idea -- the problems of Bleach lie in the industry in which it was created, as evidenced by One Piece and Naruto. See, every good story has to have an end, the problem is that when you're making something like a manga for a weekly like Shounen Jump, you get picked up for a few weeks while they test how good your piece is, what it adds to the sales of the comic, etc etc.
The problem this brings is similar to the problems faced by The Legend of Korra -- in the middle of creating what would be the middling/ending points of your series you'll get a request for more. So you have to make more and that means changing the story to fit within the time frame you believe you'll keep the job. And like most 'time assumed' jobs, the moment that your product isn't selling or gelling well with the rest and adds nothing profit wise to the equation, its bye bye.
Add to that the fact that -- for the most part, the industry is only JUST NOW (somewhat) ceasing to revolve around 'kawaii ugu' girls and panty upshots and you've got a shifting industry eager to change, remove and cut off what don't work no more.
In short, Bleach's problem wasn't its ending now.
It was that it didn't end after they got rid of Aizen, the fan favorite villain. Kubo got to take down Aizen and then probably was told 'nope, we want more' and kept it going.
Not just that, but the rules of the universe continually changed in ways that made the more 'serious' fans care less and less. Remember Sword Art Online and Attack on Titan? Their major draw ins for many of the older and more serious fans were that people could
actually die -- and not just side characters and mooks but major, serious characters which means the story could turn on its head at any given moment.
That interesting plot point was removed from both shows and -- hysterically in all three cases it was in the same exact way: They made their MC the next coming of Christ and removed all likeability and tension.
"Oh, Kirito can bring back the fucking dead AI that's an immensely complicated program that he has no possible way of knowing about?! BUT CAN'T TURN THE LOG OFF BUTTON BACK ON OKAY SURE LEMME JUST LEAVE RIGHT NOW."
"What was that, everyone's a titan now?! Great, cause THATS what I wanted to see."
"Oh, Ichigo's a shinigami, now he's a quincy and the only interesting and second most sexy character is stuck in a chair. Good fuckin god."
(And in each case, if the writers themselves had gone for it and really dedicated themselves to upping the tension, these would have been fantastic twists rather then asspulls. But they ended up being asspulls.)
More then likely Kubo was while building towards a better enemy (See: Soul King) and was told, 'okay, shutter this shit cause it ain't selling no more'. This is even hinted at more (in my opinion) by the return of fan favorite Grimmjow, perhaps as one last bid to save things or get a few fans back on reading. No avail.
[HEADING=1]TL;DR[/HEADING]
As a writer, you have to either keep up the tension and likability or shorten the story. Hence why you've more then likely skipped everything up til now -- you wanted a short, sweet, satisfying conclusion because there's no real tension in this post and you don't have the time or patience to read that flowery crap.
Power creep and over-extension of length kills tension in a story and manga industry that's already looking to cut out the eye that offends it. The endings were quick cop outs is all. More then likely both artists were already either interested or planning to do different things since more tension (Tokyo Ghoul), action (One Punch Man which cashes in on the bright emotional energy and high action movement of the Marvel series) or nostalgia (Boku no Hero Academia for Hunter x Hunter fans + also cashing in on Marvel's bright superhero genre) orientated manga are taking center stage over the original 'big three'.
Here's hoping the best to both Kubo and Kishimoto.
[HEADING=1]ON TOPIC[/HEADING]
Ended Naruto with the issue in which the village was attacked by killing Tsunade, having Sakura step up and become Hokage while Naruto and Sasuke teamed up to take out whatever villain they were fighting at that moment (I was literally so annoyed with this thing that I stopped paying attention at this point.)
For Bleach.
1. To finish it: Either end Bleach after Aizen's defeat.
2. To extend it slightly longer: Have Aizen take the throne of the Soul King almost directly after his capture ((which is something that Kubo may have been leading up to as we see Aizen possibly breaking some of the locks which kept him in the chair))
3. To keep it going for a while: Have the Soul King twist revealed earlier, have you-know-who be the traitor some people thought he would be, get the throne and have Aizen glower, get pissed and end up having Ichigo try and take on the Soul King, fail, Aizen get even angerer because 'This is literally what I've been training you for and you fuckin failed me' and see where it goes from there to possibly having them team up in the end.
Also, make the comparison between Ichigo as an anarchist and Aizen as a wannabe king a little sharper by Aizen bitching about not getting the throne and Ichigo deciding to destroy it since its the cause of all this.
Or, lastly, have Aizen pull a Doctor Doom and decide that even being a God is
beneath him and aim for even higher after killing the Soul King.