This seems like a very interesting OM, should be really fun to play. I thought of something that I think has a lot of potential:
Kyurem-Black @ Life Orb
Ability: Teravolt
EVs: 20 Atk / 252 SpA / 236 Spe
Mild Nature
- Blizzard
- Fusion Bolt
- Earth Power
- Iron Head
Kyurem-Black has decent/good matchup against a lot of weather abusers, and it is one itself with Blizzard. Blizzard is awesome under hail, althogh it is annoying when hail isn't up. Fusion Bolt hits Water-types not named Swampert or Gastrodon (hm Mega Swampert might also be good), which is most of them. It also resists Water, which is nice. Earth Power is good for Fire-types trying to abuse sun, as well as Steel-types. Iron Head I think is pretty good for the last slot on this set, since it hits Ice-types. Overall I think Kyurem-Black will be really good and definetly worth trying.
Mamoswine @ Focus Sash
Ability: Snow Cloak
EVs: 252 Atk / 4 Def / 252 Spe
Jolly Nature
- Stealth Rock
- Earthquake
- Ice Shard
- Knock Off
This will be so good for getting up rocks in hail. Snow Cloak is also really fun. It is similar to Frosslass in how it works, except that we now get up rocks, which is really difficult to get up with most setters if an Ice-type is in the lead on the opposing side.

Kyurem-Black @ Life Orb
Ability: Teravolt
EVs: 20 Atk / 252 SpA / 236 Spe
Mild Nature
- Blizzard
- Fusion Bolt
- Earth Power
- Iron Head
Kyurem-Black has decent/good matchup against a lot of weather abusers, and it is one itself with Blizzard. Blizzard is awesome under hail, althogh it is annoying when hail isn't up. Fusion Bolt hits Water-types not named Swampert or Gastrodon (hm Mega Swampert might also be good), which is most of them. It also resists Water, which is nice. Earth Power is good for Fire-types trying to abuse sun, as well as Steel-types. Iron Head I think is pretty good for the last slot on this set, since it hits Ice-types. Overall I think Kyurem-Black will be really good and definetly worth trying.

Mamoswine @ Focus Sash
Ability: Snow Cloak
EVs: 252 Atk / 4 Def / 252 Spe
Jolly Nature
- Stealth Rock
- Earthquake
- Ice Shard
- Knock Off
This will be so good for getting up rocks in hail. Snow Cloak is also really fun. It is similar to Frosslass in how it works, except that we now get up rocks, which is really difficult to get up with most setters if an Ice-type is in the lead on the opposing side.