Ekans-Arbok: Going by its description, I would like to see a Dark-type, boa constrictor like variation.
Paras-Parasect: Rather than Mushroom taking over, Paras could get into a symbiotic relationship with the Shroom.
Shellder-Cloyster: Despite being an Ice-type, Cloyster has appeared in several tropical climates. Instead, the new Cloyster can be part Rock and have access to Power Gem with its pearl.
Drowzee-Hypno: A two typed variant would be cool, something like Psychic/Ghost or Dark.
Tentacool-Tentacruel: A part Psychic variant would be cool.
Corsola: A higher BST variant would be cool.
Huntail-Gorebyss: Just give them their Dark and Psychic-type, please. Also give Clamperl Psychic type as well.
Chatot: A Water/Flying variant with Skill Link(it gets Metronome as a held item) or a Dark/Flying variant that lives in inner jungles would be cool.
Shellos-Gastrodon: A Water/Rock variant or Bug/Rock variant based off its ancestral hard shelled variation would be cool.
Dweble-Crustle: I would like to see a Bug/Water variant that uses a regular seashell.
Inkay-Malamar: I would like to see a Water/Flying variant that acts like a regular flying squid.