Then what is there that was actually based on Herbert senior's notes?
Probably very little, if the notes in fact exist (I personally believe they do exist, just that they were not followed, and that they were probably very minimal). Some here believe that one thing from the final books that does seem like something FH might have written is the idea that the Honoured Matres were descendants of Tleilaxu tanks - that's a good idea, so maybe FH put it in the notes, and if not, if KJA and BH made it up themselves, then good work I say, one of their very few good ideas.
Also, it seemed perfectly fine to me for Idaho to be a KH. It just wasn't treated right, because they played with the idea of KH like a toy.
See what Ampoliros wrote about this, I agree with his take on it based upon the last 2 novels FH wrote.
Plus, I wouldn't play down a KH too much; Paul (the grandmaster's creation) was able to operate without eyesight by abandoning everything else in favor of the prescience trap. Leto II, by way of both paternal and maternal ancestral memory, was of an intellectual pluck that set him on a pedestal above everyone else for thousands of years
You completely missed my point. I'm not playing down a KH, I'm playing down the power of a KH post-LetoII. LetoII's intellect didn't just come from having those ancestral memories either, he had powerful prescience and used it often, and he wasn't just a KH - he was a hive mind. He allowed himself to be possessed by a massive swarm of dead personas, so he didn't just have ancestral memory in the way a KH or BG does, he had access to it like it was his own memory, and he was a composite personality of all those people as well as himself. That, combined with his prescience is what made him so powerful.
But after his Golden Path was in place, a KH would be reduced to simply "double a BG" by virtue of having access to both lines of ancestral memory, his prescience would be basically useless.
Also, there'd be no real point to the KH in the way that KJA wrote it (lets not kid ourselves, BH's contribution seems to be minimal based upon the writing style and how fast we know KJA writes versus BH) - after the Scattering the idea that the ultra-KH (what does that even MEAN?!) could somehow reunite humanity is both impossible and also goes against the whole point of what FH was trying to teach us (the readers) with the Golden Path.
Also, if you read the final two books, KJA completely had no understanding of what the Scattering was. AT ALL. He didn't understand even remotely how big it was or what it's purpose was. Of course, given his extremely limited grasp of science itself I'm not surprised, I'd be surprised if he even knew what a galaxy was versus a solar system versus a universe, and the distances involved in any of that.
So, since when did they one-up Herbert senior? I mean, you can say that they were crap writers, but Idaho was bound to be a KH anyway, right?
No, not "bound to be a KH". It's not something I can rule out 100%, but it's highly unlikely that that was where FH was going with Duncan based upon the last 2 real Dune novels.
When did they one-up him? Always, constantly, it never ends in their writing. FH had a KH, KJA writes an ultimate-KH. FH wrote about Leto II, a near-god to teach people to stay away from gods and to stay away from centralization, KJA writes Norma Cenva, an actual god-being who teaches the exact opposite, that humanity is doomed without a god to save them, and that with the ultra KH humanity needs to go back to centralization.
There are endless examples from their books where everything they write just has to be bigger and cooler than the originals. They even threw in a sandworm made out of several sandworms combining into one (kewl, a new super power for sandworms!) that according to the authors was bigger than any ever seen before (which was a mistake on their behalf also, because the size of those worms that combined is spelled out in the books, and I did the math, their combined size wouldn't come close to even HALF the size of the worm that Paul first rode back in Dune).
Seriously man, more lasers, more explosions, super heroes that are more super, that's all KJA can come up with. He can't come up with any kind of serious plotline or character that is/are compelling on their own.