This could be used to do things that would be very interesting or useful for testing, like:

• Execute only the read or write side of a workload
• Reformat operations to execute writes using legacy GLE, write commands, bulk writes, OP_COMMAND, etc.
• Modify the outgoing readpreference, readconcern, or writeconcern for executed operations
• Attach metadata to outgoing operations ($comment, maxTimeMS, maxScan, snapshot, batchSize, etc)

The user might want to do these things per-namespace, per-op type, or some other set of specific constraints.