I don't know if I can suggest this, but I've actually got an idea for an achievement.
Have you ever read any of the XY or older smogon pages for Luvdisc, Farfetch'd, Unown, Castform, Spinda, Delibird (mostly the BW and older ones), Pachirisu, Furret (mostly the BW and older ones), Kakuna (especially the DP one) or Ditto?
They're pretty damn funny and mostly just go on and on about how bad they are, which made me think it could be kind of fun to try and win with them.
Basically, the achievement would be winning with a team that has 6 of these pkmn and could be called something like "the unpopular kid" or so
(I don't really care about the name of the achievement, should it become one. This was just the best I could come up with at the moment)
Hoppip (the BW one), Sunkern/flora and Magikarp's analyses are also pretty hilarious, but they didn't seem as "OU relevant" (lol) as the others.
In fact, sweeping with a Magikarp might just be an achievement in and of itself. Something like "never done before...". Too bad BP got nerfed though
I don't know if this would make a good achievement, but it sure would be fun trying to win with a team like that, so I might just go ahead and try it anyway :p
EDIT: another one I thought of was winning a battle with all EV's and IV's set to zero and a neutral nature for all pkmn.
I don't know if adding achievements is something we still do, but I had some fun ideas over the weekend, so I thought I might as well share them