Few things to take note are these: Perhaps you know most of it already
1). If are going through a lot of crowd, keep your camera inside and use the full lock of the back not the safe flap over. It doesn't matter if your camera is worth just 50 bucks. If it looks foreign, it is "costly" there depending on where you walking. You mentioed Holy, that is why I suggested being this careful.
2). If you are hiring a guide, you will want to check with other photographers/reputed hotels to get some contacts. Do not hire anyone that comes to you. I am not familiar that much with North India. So I can't help you there. There is one person I usually contact in South India and have a lot of success with that.
3). Humidity changes from north to south and mid west India is a lot. Take care of your equipments.
4). Travel light. Check-in only one bag and carry your camera and all equipments with you on plane. Make sure to take some backup clothes in your carry-ons case your check-in is lost/arrive late.
Realistically speaking, when I go I pick 1 city for the 1 week. Even then it is such a hastle. So covering that much will be exhaustive.