Shoshone split idea:
Comanche
UA: The great expansion
Horses provide double quantity. Founded cities claim all workable plains,buffalo and horse tiles. Per each horse, one unit is

maintenance free.
UU: War chief
Replaces great general. Unlike the great general which it replaces, the War chief is only effective during wars. The war chief has 1 extra

movement compared to the great general, and doubles the

gold adjacent units get from pillaging tiles. It provides extra 10% bonus against

barbarians.
UU: Comanche Raider
Replaces cavalry. Much faster then the cavalry

c5moves: 6), and has a 20%

strength while attacking other unit. When stationed on a tile with horses, the horses count as yours(regardless of the tile owner).
Shoshone
UA: Snake Indians
Units move through plains as if they were roads, and ignore terrain costs on tiles adjacent to mountains. units receive +15%

combat boost per each adjacent unit from civilization you share common enemy with. +1

movement for civilian and melee land units during war(until the industrial era).
UU: Band
Replaces settler. Unlike the settler which it replaces, the band has

combat strength(based on the strength of mounted units), and may remove buffalo(for

food and

culture) or horses(for

production) from tiles for ten turns(may not remove resources from the same tile twice, or from a tile adjacent to a tile that resourcds has been removed from).
UI: Shoshone encampment
May only be built on plains\grassland. +1

food and

production, and +1

culture per each adjacent mountain. If adjacent to other terrain types(not grassland and plains), provides +1

culture.
(Feedback, pls.)