What is the difference between this idea and exposing a read-only MongoDB (JSON in, JSON out) via HTTP endpoint? In the end, 50 ranged HTTP requests is not that great for unstable connection, 1 request is way better, and you need a server anyway.

Okay, offline first, what does that mean? Should I download the entire 600mb SQLite database? Should I do it every time it changes? Who will pay for the bandwidth? We can not employ standard HTTP proxy and caching mechanism here, it is not for 600mb files.