I'd see if you can easily port the on top of browser based sqlite in wasm, that's expand your user base and lead to some of the "holy Grail" in the offline first/sync systems
b) You can't use IndexedDB on the server, so you wouldn't be able to write sync code that runs on both the client and the server
Modern offline-first applications include a local backend every bit as complex and demanding as a server-based backend.