It would be a neat addition if the underlying LevelDB could be replaced with a different DB to allow read access by other clients. Ideally this would be a pluggable interface to allow implementations for all kinds of DBs (e.g. Mongo, MySQL)

Developers would need to make sure to only use Read-Access to the Tendermint-handled Tables/Documents to not corrupt data.

Two benefits I can see so far:

• no redundant data storage (currently TM-Node + NodeApp store semi-redundant data)
• easy query with SQL/NoSQL syntax (depending on used DB)

Drawbacks:

• possibly performance