Ariados:
Atk +50
Type: Bug/Poison -> Bug/Dark
?Ability: Adaptability
Reasoning: Unique typing, makes up for low speed with stab sucker punch.
Armaldo:
Def +30, SpD +20
Ability: Regenerator
Reasoning: Better bulk, patched up recovery, has decent typing and offensive stats already.
Bibarel:
Atk +20, Spe +30
Reasoning: Not much can be done, has a useable speed tier and more Atk to take advantage of Simple Swords Dance.
Butterfree:
SpA +20, Spe +30
Type: Bug/Flying -> Bug/Psychic
Ability: Adaptability
Reasoning: Confusion might as well be its signature move, Adaptability counterpart to Beedrill.
Delibird:
STATS
Ability: Prankster
Reasoning: Prankster spikes and DBond give it a unique niche.
Dewgong:
Atk +50
Ability: Technician
Reasoning: Aqua Jet, Ice Shard, Icicle Spear get huge damage boosts. Also boosts Fake Out (and Frost Breath for what it's worth).
Fearow:
Atk +30, Spe +20
?Ability: Tough Claws
Reasoning: Good Atk, very good Spe. Tough Claws could patch up its lack of held item if necessary.
Furfrou:
Atk +10, Def +40
Reasoning: Massive defense increase, that's about it.
Ledian:
Atk +20, Spe +30
Type: Bug/Flying -> Bug/Fighting
Ability: Pure Power
Reasoning: Huge Power mon with good speed, everyone wants to see Ledian hit things properly.
Luxray:
Atk +15, SpD +10, Spe +25
Type: Electric -> Electric/Dark
Ability: Strong Jaw
Reasoning: Everyone wishes Luxray was Dark type, has access to elemental fangs and Crunch, Thunder Fang is cooler than Wild Charge.