Gandhi is always available as the leader of India in all Civilization games. The upcoming expansion to Civilization VI, Rise And Fall, will add an option not to pick him with the inclusion of another leader to choose from, Chandragupta.
Chandragupta was the person that managed to unite most of India under one rule, and his leader ability reflects that. “Arthashastra” will allow India to declare War Of Territorial Expansion early (which grants lower war weariness), plus extra movement and combat strength just after declaring war.
Add that to India’s existing ability which includes lower amenity bonuses to anyone at war with India, the Stepwell improvement and Varu, elephant siege units, and India under Chandragupta will be even more menacing than Ghandi’s nuke-happy AI could ever be.
The base game in Civilization VI had only one civ with two leaders, the Greeks. Rise And Fall should increase that tally with more leaders for existing civs, as well as completely new ones when it launches on February 8 for the PC.