[Edited by 2015applicant on Dec 11, 2014]
ISB and other ranked business schools in India are notoriously competitive and admissions is highly selective.
The current PGP cohort at ISB has an average GMAT of around 710 I think and average work experience is something like 5 years, so I think that barring something really interesting about your profile, your chances are pretty low.
Are you considering programs outside of India?
I share your skepticism. Indian employers don't need to recruit non-Indians. Many overseas-born Indians are not able to operate in a top-tier IIM-type school because of their different training. If the admissions managers says that you stand a chance then I would jump with both feet in her direction. I would be surprised, but perhaps you have some other qualities which make you an interesting candidate? But ISB is harder to get into than Cass or Manchester...
Yes, I would. No point studying in one continent if you want to work with another, unless your strategy is to be hired by the HQ to return to a subsidiary country you know well.