On second thought, this isn't too bad of a start. I'll give some more detailed feedback. Replace Arceus and Darkrai with primal Kyogre and Regigigas because they pretty much do the exact same thing but better. Your Garchomp doesn't work in BH, so replace it with Giratina to switch into attacks that are super effective against your other Pokemon. Give Gyarados unaware and careful to tank other simple users. Replace its darkest lariat, ice punch, and waterfall with knock off to remove items, spectral thief to steal stat boosts, and u-turn for momentum. Give Groudon contrary to abuse v-create and an earth plate and adamant for more power. Replace all of its moves with v-create and thousand arrows for STAB, sunsteel strike to cover fairy, and u-turn for momentum. Give Blissey 252 HP/0 Atk/252 Def/0 SpA/252 SpD/0 Spe so it can still work if imposter ever fails. Replace its moves with trick to get rid of the choice scarf, recover to heal, spikes to lay hazards, and whirlwind to deal damage with spikes and reset stat boosts.
