I am back for my next round of speculation, which is why I joined here in the first place.
1. Dunsparce
The obvious candidate.
Dunsparce has the movepool that would make an epic sweeper or wall, yet it lacks the stats to really make effective use out of it.
I would like it to become a Fairy/Ground-type upon evolution, like I mentioned in the past. With better abilities like Intimidate and Sheer Force, coupled with a BST on par with Arcanine, Dunsparce would become the majestic, yet stronk godly snek we've dreamed of for years.
2. Castform
I would imagine it becoming a Normal/Flying-type cyclone with a unique Ability that summons a random weather condition that alters it's Normal-typing to correspond with the conditions of the weather that is summoned.
3. Corsola
A natural means of properly standing up to Mareanie and Toxapex, I would give it a more confident, yet spooky appearance, alongside the Water/Ground-typing. It's branches are sharper and would be surrounded by cracks underneath that would allow it to send seismic shockwaves to ward off it's poisonous predators. It would still have to compete with Gastrodon and Quagsire, but it can have it's uses.
4. Delibird
It is established to be the Pokémon version of Santa Claus. The Santa motif would be heavily emphasised should it evolve. It would a slow and bulky Ice-type to prevent it from being busted, since it has access to the Hustle Ability. It would learn Roost for some recovery. I would envision it being an Ice/Fairy-type, given that Santa is a mythical figure, but Ice/Flying would be fine by me, since it has STAB Aerial Ace, which can work exceptionally well with Hustle.
A good Ability for it would be Snow Warning, since it has access to Aurora Veil.
5. Farfetch'd
The Spaceworld Demo shows that it was meant to evolve. If Tangela can still get an evolution long after that beta, so could Farfetch'd.
While it is meant to be a scam to players, it has every right to be a candidate to evolve. It would have a new type of stick that boosts Grass and Bug-type moves, since it has access to really good moves like Leaf Blade and First Impression. It would be a swan that acts like a samurai, similar to it's beta evolution.
6. Komala
Comatose is too good of an Ability to waste, but I can see why it would not evolve. Even so, it still has the potential to become a beefy koala that would be a mix between Pangoro, Conkeldurr, and Snorlax. It show no mercy, even in a deep state of slumber. It could become a Normal/Psychic-type, since Musharna and Drowzee are associated with the power of dreams.
7. Jynx
Mainly to complete the elemental humanoid trio it seems to be a part of, alongside Magmar and Electabuzz. Some ideas I've seen floating around includes a Valkyrie specialising in the power of opera. I would imagine it becoming some sort of Snow Queen or Blue Diamond-like figure, yet retaining it's yellow and purple colour palettes.
8. Chimecho
Mainly to have a requiem bell Pokémon. It would become part Ghost-type to partake in many spooky ghost parties, especially in haunted mansions. It would have streamers, a cape, and a steel bell for it's tail. It would be more feminine in appearance, but it would be nice to have a spectral princess Pokémon.
9. Heatmor
While it would be unfair to leave Durant out, at least the ant has good stats and Ability to be a dangerous physical sweeper. Heatmor has access to a new move called "Fire Lash", which is a great new move, yet it doesn't have the stats to pull it off.
I would like it to become a Fire/Steel-type when it does evolve, since it has a lot of pipes on it's body. It would have Sturdy or Filter as it's Ability to better stand up to it's prey.
To ensure Durant is not left out, I would see it getting a Mega Evolution, since it's already pretty strong itself. Mold Breaker would be a fantastic Ability, although it would heavily complicate the predatory relationship both Pokémon have.
10. Meowstic
Mainly to show that the Espurr line can only hold back their immense psychic power for so long before their ears grow tired of restraint. I would see the female becoming a powerful Psychic/Dark-type with a terrifying Sp. Atk, while the male becomes a bulky Psychic/Fairy-type. Their movepools may not change all that much, but both would learn Focus Blast and Moonblast for better coverage, as well as Moonlight for some recovery.