Litestream author here. Currently we're handling the "single writer" issue outside of Litestream. We have controls in our internal systems that make it work well. But yes, the lease PR is the direction we're looking at going.

I'm not sure you can have readers see something separate than writers. When SQLite promotes a read lock to a write lock under WAL then it checks if any of the data has changed and then fails the transaction if it has.