He's right on with the lead acid batteries. You're going to need power that will last through hours of the electricity being out. You should be able to find lead acid batteries as part of an IPS solution. I'd also suggest a diesel, petrol, or natural gas generator. Solar isn't going to do you much good on a rainy day when the electricity is out for 12 hours straight.

Wait a minute.... don't fonts like Devanagri and Bengali already support stackable consonants? Font Chart of Conjuncts in Bengali