A nice feature to have is the ability to start printing structured messages (json) to stdout/file pipe/socket while keep sending all data to the Kafka cluster. This is extremely useful for live debugging, assuming there's a handy way to start/stop this behavior at runtime (eg. sending a specific signal to the process).
As commented by @Vgutierrez we should be careful about eventual PII that could be written on disk (or journal in case of stdout) and about performances too (one of the biggest issues with Benthos regarding this).