Volt Switch Movement! (#UnovaForSmash)さんのイラストまとめ

Stage hazards (2):
Sometimes a Pokemon may fly/jump up from the dark grass (see layout above) or rightside pond, to lift up a platform (respectively a tree branch held up with Magical Leaf or an ice platform) that'll disappear after a while.

Here's all the stage cameo 'mons:

Finally, the boss of the Classic route: Rayquaza comes back from Brawl! (including its boss stage)
With "Decisive Battle! N" playing, as a reference to N using the Dragon type Reshiram/Zekrom.

Alternatively, Rathalos could be the boss, with "Battle! Reshiram/Zekrom" playing.

(Alternatives:
Alt music: Death Mountain (The Legend of Zelda)
Alt colors:
-P1/P2 is default Tepig: "shiny" Tepig
-P1+P2 are default+shiny Tepig: "Bidoof" Tepig
-P2 is default Charizard: "former shiny" Charizard
-P2 is default Incineroar: "shiny" Incineroar)

Round 5: Fire & co.
CPUs: solo Tepig (Professor's) & Charizard (Trainer's, Fire/Flying), & Incineroar (Fire/Dark)
Stage: Bridge of Eldin (Ground/Rock-like plains, hazardless)
Music: Crag Area medley - Rockridge Fort half only (PokePark 2)

2/3 full evos, but all of them hit hard!

Alt scenarios:
Alt music: Frozen Hillside (Kirby Air Ride)
Alt colors:
-P2 is default Squirtle: "shiny" Squirtle
-P1/P2 is default Oshawott: "shiny" Oshawott
-P1+P2 are default+shiny Oshawott: "Emolga" Oshawott (Emolga's weakness is Ice)
-P2 is default Greninja: "Shiny" Greninja

Round 4
Stage: Summit (Ice, Water/Dark depending on transition)
CPUs: separate Squirtle (Trainer's) and Oshawott (Professor's), and Greninja (Water/Dark)
Music: Crag Area medley (PokéPark 2) - Colosseum half only

Amping it up by having 1 of the 3 opponents be fully evolved!

Hypotheticals:
Alt Stage: Prism Tower (doesn't start sky high)
Alt music: Lumiose City
CPU if P2 is default Pichu: Spiky-eared Pichu
CPU if P2 is default Pikachu: Pikachu Libre
CPU if P2 is default Emolga: "shiny" Emolga
(Emolga in this round depends on the hypothetical scenario)

Round 2 is against the separated grass starters Snivy (Prof's team) and Ivysaur (Trainer's team, also poison), on the pack's own stage, the Abundant Shrine (whose forest setting is associated with grass and bug types)

Lostlorn Forest plays in this location just like in BW(+2).

And here's the last remaining set, the Sonia and Shadow Pokemon colors. Most recent Professor and an old mechanic's recent comeback, a neat combo.

Not Dynamax energy, but the Shadow Pokemon colors do ressemble that of the source behind it (that Sonia also does research about).

Almost done! Next is the Kukui set of Pokemon Professor colors.

All of the 'mons's colors range from uncommon to legendary, with Snivy as the legendary Giratina, Tepig as the rare Zorua, and Oshawott as the uncommon Emolga.

Why lategame 'mons for Kukui? ... Sun/Moon spoilers.