"John Company" began some 15 years ago as a rules project solely for the Sikh Wars, but grew to encompass a wider period and range of technologies.
That said, the research on the Khalsa represented there is very thorough--if not yet truly complete--and draws upon sources gathered from around the world.
In short, believe me or not as you may prefer, but virtually all you need to know for pitting the Khalsa against the Brits/HEIC is in the resources section of the rules.
The rules, in their Second Edition, are the only ones designed from the ground up for India and its many armies, and not based on any other game system mashed and twisted to fit, and the peculiar strengths and weaknesses of the Khalsa, and the other armies, are addressed in ways not possible in other systems.
Okay, you got me! I'm proud of our work, and at the risk of sounding the merchant, you won't find a more authentic or complete set of rules anywhere.
Feel free to ask around here at TMP from customers who will give you there honest opinions. You might also run a search string on "John Company" and look for the detailed review of the first edition written by Chick Lewis and posted here a few years back.
TVAG