Live partial pipeline updates

Following the nice new feature to allow dynamic configuration reloading as described in #4513 and PR #4520 I suggest the next step is to provide and API for dynamic partial updates to a live pipeline.

This would allow, for example, to dynamically update the filter and/or output stages without altering/stopping the input stage providing the ability to change a configuration without loosing any input when paired with variable length persistent queue.

This is an idea & discussion issue. If this idea has leg we can followup with a design issue and/or POC.