Short answer - yes, CELTA plus a degree (from an English-speaking country) would be useful. But it will be very very difficult for you to get a TEFL job in India - or at least one which pays anything more than a very basic wage - without several years' prior experience in addition to formal qualifications. More to the point, those without an Indian passport or Indian ancestry will find it hard to get a working visa unless they are VERY well qualified and experienced - India already has a lot of people who can speak (and teach) English very well!

Having said that, your work in Engineering might give you scope to 'specialise' in a particular area and work 'in house' for one of the big Indian companies helping their staff to improve their English - I'm sure those roles do exist as the financial firms that have off-shored facilities to India do sometimes have their own small 'schools' in order to regulate who gets offered a job where they'll use the language every day. You might want to look at the individual websites of those companies to see if they do have these types of role and if CELTA (and other qualifications) are required to apply