Things that I would like even though it's not going to happen:
1. Pokemon that can evolve should probably evolve fairly early in the episode and then spend the rest of the episode focusing on its new form even competing in a PWC that barely raises Ash's rank so like by three spots. So from 949 to 946. The exception would be Quilava which should get some cool training in and some great screen time maybe even a PWC and then evolve and then continue to a presence for a few episodes.
Pokemon that I want to see evolve the most: Gible, Quilava, Totodile, Snivy, Palpitoad
2. Pokemon that need the screen time more like Typhlosion should definitely necessitate a few more episodes. After all Typhlosion has gotten the raw deal and could use more appearances. My only issue which I don't care is that its ANOTHER fully evolved fire starter, but in fairness it is Ash's only pure fire starter, since he didn't get Scorbunny.
3. If Ash will get Garchomp, I'll want Gible to evolve really quickly and then Ash uses Gabite for like 10 or so episodes and then have it evolve into Garchomp.
4. Pokemon that need screen time that can show up for a single PWC battle are where they at least beat a Pokemon: Kingler/Muk (1st generation), Donphan (2nd generation), Glalie/Torkoal (3rd Generation), Torterra (4th generation), Unfezant (5th generation), Noivern (6th generation), nothing for 7th generation for reasons I'll get to.
*NOTE* As you noticed the Pokemon I listed were NOT the most important Pokemon. I chose Pokemon I felt like got robbed the most, and would just be good to show off at least one massive victory. Major players will be different.
5. Reserves that need to participate in strong past generation battlers (including rivals): Charizard/Snorlax (1st Generation), Potential Typhlosion or Heracross (2nd Generation), Sceptile (3rd Generation), Infernape (4th Generation), Krookodile (5th generation), Greninja (6th generation), Incineroar / Melmetal (7th generation)
6. Pokemon that would be nice to get some battles or just really good appearances but aren't super important to me: Bulbasaur/Squirtle/Tauros (1st Generation), Bayleef/Noctowl (2nd Generation), Swellow (3rd generation), Staraptor/Buizel/Gliscor (4th generation), Oshawott/Scraggy/Leavanny (5th generation), Hawlucha (6th generation), Lycnaroc/Rowlett (7th generation).
Now if you noticed I really kind of left Boldore out (and other more meaningless Pokemon but Boldore does stand out). Look I would love for Boldore to come back and evolve into Gigalith. I don't know of anyone who prefers Boldore to Gigalith but I'm sure someone does, but I really want Gigalith. But I left it out because I just do not see it happening. Unless they want to introduce an anime only concept of evolving trade Pokemon without needing to trade.
If they do ignore reserves completely and I mean completely not even bringing back Gible and fully evolving it for example. Then there would be no reason WHY they shouldn't have Ash catch a lot.
At a certain point it's going to be annoying seeing Pikachu, Dragonite, Gengar, Lucario, Sirfetch'd, "Rillaboom" being used in EVERY single battle of the PWC including potential battles against Paul, Tobias, etc, etc.
So Ash might need 12 new captures to justify not using reserves. So he has around 2 team compositions well actually he only need 10 captures since Pikachu will take a slot. But I think 12 would be nice.