Your premise, however, is flawed. Kusaka is able to do all of these things because he has
freedom. It's very clear the manga isn't as executively meddled as the anime. Kusaka doesn't have a whole committee breathing down his neck, he doesn't have to work with 3-5 other writers, or animators, or a director who's above him and get it passed through things that has to air on television, which in and of itself brings more restrictions.
Because Kusaka doesn't have those, he can craft a story
his way and no one else's except for input from an editor and possibly his artist. That offers a lot of possibility that the anime has to actively work around. Not to mention that the anime is, moreso than the manga, made to
market the games. They have to show all the Pokemon and have to sell those games. They also have to produce it on a weekly schedule. What's Kusaka at now? Monthly. That's
way more time than the anime.
I'd argue, in the end, that if Kusaka had to work with the same limitations as the anime staff, he'd potentially produce even an
inferior product.
To address your individual points briefly:
- You say an in-depth look would be provided and the plot would move every episode. That's really easy to say when a chapter could maybe fill 5-10 minutes of an anime. Now try 20 minutes for 3 years and a total of 140 episodes. That's 280 chapters produced by equivalent at least. You're definitely going to be seeing either filler or a downgrade in quality.
- I've read each installment of the manga, and I can't say it's done anything better than XYZ battles, especially since the rules between the verses are different, so this point is highly speculative.
- Side characters only being the trainer classes would get very boring after a while and leave nothing for original characters; we'd have never had a Sawyer or Alain or Meyer, all of whom were fantastic characters on the whole.
- "Satisfying conclusion" is up for debate as well, because both DP and XY got really great conclusions that were satisfying for the most part.
No offense to the effort you put in, but all of your posts feel like they're saying the anime
needs to take from the manga to be good, when, in fact, it doesn't. They are two very different identities and very different properties that wouldn't mesh with each other. Perhaps Ash's journey has gone a long time, but we've seen him grow from cocky noob to a genuine ace trainer by XY and it makes whatever accomplishments he has feel
fulfilling. You can't always get that when you jump protagonists every few years (note, I said always). It's an entirely different beast from the manga, and perhaps better for it at times. I certainly didn't connect to the XY arc of the manga, which felt by the numbers and full of so much doom and gloom I got hit with Darkness Induced Audience Apathy, while XY in the anime gave me a culmination of everything to that point. So you can't objectively put one over the other.
Bottom line after this winding post: Kusaka with the same restrictions the anime creators have may not write a good series, and may, in fact, produce something worse. However, we'll never know, because he's not an anime writer, and I doubt he ever will be.