But then rolling back the entire batch would potentially rollback inserts/updates/deletes from multiple independent requests.

I need to bne able to rollback just the queries of a single request.

You don't need to rollback, because you have already checked the invariants and the system is a single writer.

Ah you're doing request response? sqlite/single writer fits much better with a CQRS still approach, so in my experience you move away from request/response to something push based. That being said even in a request/response model wrapping a request in a transaction is not a great idea. The minute you have anything that takes some time (slow third party) that transaction is going to sit open and cause trouble.