I'm curious as to how useful this will be. Tying it to SQLite makes it portable, but abstracting it so that it can be used with any db would be far more powerful. Why? Because the SQLite implementation is enough to get it working in the browser, but it does not make WordPress 100% SQLite compatible. For example, a WordPress site built on MySQL can't be migrated into an SQLite powered WordPress using a common migratio…
Out of curiosity, how recently did you try?
We're using a new SQLite integration that seems to be pretty good at translating SQL to SQLite: https://github.com/WordPress/sqlite-database-integration
We'd be curious to learn more about how it failed. It's definitely an area we'd like to improve.