Thanks for the response!
I looked into your suggestions and it seems most suitable for me to keep using actors. However, I still wish to use akka-stream for communicating between FRP worlds.
The example you sent does not use akka-stream. Would it be easy (and make sense) to combine the two?
Some input/output vars are intended to be consumed/produced in other places (e.g. synchronizing state over WebSocket). Other inputs/outputs are intended to be rate-limited, not necessarily by the producer.
So I think my question boils down to: how I can make actors with (conceptually) multiple streams between each other, each stream having customizable throttling/rate limiting?