I’d like to add to @gbiggs that this is a very time sensitive request for input. This design needs to be solidified in the next 1-2 weeks in order to be done in time for the Crystal release, so if you have input, please take the opportunity to speak up now. Thanks!
Also, if you want to volunteer to help with the implementation, chime in here too. We may be able to do some divide-and-conquer. I was planning to help in the rclcpp layer for example.