Exactly! The greek roster for bactrian didn't exist at that moment, but the indo-iranian roster was always available! For example for the Battle of Hidaspes, the army of Porus can be somposed by Elephants, Sreni Pattya Yoddaha (Heavy Infantry), perhaps Taxilan Agema, Hindus Patiyodha, Hindus Pattisainya and Kamboja Asvaka Ksatriya. It would be good to include chariots in that army.