OK I'll look at the BatchingExecutor. The iteratee library sits outside Play core and doesn't have a dependency on Akka, so it's not something we can use easily without reshuffling our dependencies.

Can you expand on your "consequences are many" comment?

I'll review the implicitness of the EC. If I remember, I had some sort of trick I was using to reduce the chance of errors when dealing with lots of ECs: user ECs, iteratee ECs, unprepared ECs, prepared ECs, etc. I can't remember whether it was better to be implicit (and hence get an ambiguous implicits warning) or not be implicit.

The EC is scoped to play and currently only used by iteratee code.