Here's a bit of information that might help you.
1. Can a foreigner purchase a mc and have it road ready in India? How?
- Legally, an indian motorcycle can only be registered on a local residents name. But you shouldnt have a problem as long as the paperwork is up to date.
2. Can someone help do the necessary modifications on the purchased bike for long distance touring.
If you are starting in Mumbai, I'll be able to help you with this. Will tell you more via PM.
3. What are the must see POI in India?
India has something for everyone. It depends on what you are keen on seeing/doing. Beaches, Forests, Hills, and even a bit of desert.
4. Which border crossings are not recommended to use when travelling on a motorcycle?
If you are referring to international borders, you'll only be able to cross the border to Nepal as far as I know. As for state borders, most places are safe barring a few places that might have insurgents.
5. When is the best season to start the journey (i.e.dry season)?
For the west/ south of India, January February are good months since it's not as hot as summer and there's no rain. For the northern mountains, I think June/ July is the right time.
Hope this helps.