How about this? Mainly one type, but two wild card Pokemon to cover weaknesses, and we get six Pokemon for each,
>Sidney: Cacturne, Crawdaunt, Crobat, Claydol, Pangoro, Mega Absol
Crobat is there to fight Fairy, Fighting, and Bug types, while Claydol is meant to take on Fighting types
>Phoebe: Sableye, Dusknoir, Heracross, Hariyama, Trevenant, Mega Banette
Heracross and Breloom can both combat Dark types that would threaten Phoebe's Ghost types
>Glacia: Froslass, Walrein, Gardevoir, Ninetales, Aurorus, Mega Glailie
Gardevoir fights Fighting types that could counter her Ice types, while Ninetales deals with the Steel types
>Drake: Altaria, Kingdra, Skarmory, Machamp, Noivern, Mega Salamence
Skarmory's Steel type deters Fairies, while Machamp's Fighting type can deal with Ice types
>Steven: Aggron, Magnezone, Azumarill, Breloom, Aegislash, Mega Metagross
Azumarill's Water and Fairy type can help fight against Fire, Ground, and Fighting types, while Breloom's Grass type can help against Ground types, but also against Water types that resist Steel
The result is that everyone has at least four Pokemon that are of their type and two Pokemon that attempt to cover weaknesses
Also, five of the Pokemon should all be reasonably found in Hoenn, while the odd one out is a Gen VI rep from Kalos to remind you what generation you're playing
