Hey, I know I'm a little late, but I have a couple more suggestions for achieviments:
2k18
Win a battle with a team where the sum of all Pokémon in the team is equal or less than 2018 (336.7 is the average BST).
Dex Streak
Win a battle with a team where every member's dex number is one point apart from each other (example: Bagon, Shelgon, Salamence, Beldum, Metang, Metagross).
Hot n' Cold
Win a battle by only using Fire- and Ice-type moves.
Sweet n' Sour
Win a battle by only using Fairy- and Poison-type moves.
Focus Master
Win a battle while hitting 3 Focus Blasts in a row.