I gotta say, your idea of a Supabase-like system for SQLite got me thinking. It's an interesting concept. SQLite running next to your server could certainly speed things up, but don't forget about potential issues with concurrent writes. SQLite might not be as graceful as other databases in handling those.
The dev-prod synchronization you mentioned is a neat idea. Just remember to keep things secure and don't expose sensitive data. Also, think about the size of your production database. If it's too big, this might not be the best way to go.
Having an interface to access, view, and modify data straight from the production DB would be super useful. Depending on how complex this gets, you could either make it part of the application server or set up a separate server.
Auto-backup to a bucket is definitely a thumbs up from me. Tools like Litestream can be a lifesaver here.
Have you heard of Datasette? It's an open-source tool that lets you explore and publish data from SQLite databases. It could be a good starting point for what you're trying to build.
Your idea sounds like it could really shake things up. Keep us posted on how it goes. Good luck!