I agree...its no fun. I've done a midnight international arrival at BOM with a 5am flight at the (pre-refurbishment) domestic terminal 1B, where the downstairs Jet Airways lounge was open all night and accessible with a Diners Club card. After the refurbishment, I think they did away with the downstairs lounge, and the upstairs lounge closes at some point at night.

I haven't taken more than half an hour to get through immigration and collect bags in years, even if I'm in the back of the bus. Get a cheap hotel room at the international arrivals. All include hotel transfers. If you're flying AI, they have their own hotel near the airport and will give you vouchers for the night so its free.