@mkhansen Currently we’re writing an update for @gbiggs design doc and examples of what the client library APIs should look like. Moving quickly is important to us too. I expect implementation will start in rcl in parallel with opening design and example PRs so that feedback is incorporated as we go.
I will post links to new PRs here. In the meantime https://github.com/ros2/ros2/issues/583 is a list of what is being targeted at Crystal.