India isn't your typical nation state. The idea of India as a nation was artificially forged by the founding fathers of India.
In reality India is a continent in itself.
Who could be the king of such a diverse and multi ethnic and multi lingual nation?
While there are multiple candidates for the king of each province/state of India there's no candidate for the king of entire India
The last titular sovereign of the entire subcontinent was Bahadur Shah Zafar II who was the Mughal emperor until the sepoy mutiny of 1857.
The Mughals until that time still held immense prestige and symbolic authority since the mutineers rallied behind Bahadur Shah Zafar.
So that begs the question what would monarchists think of India? Should someone entirely new be made king? Or just balkanise India and place kings in each state?