I miss the overall mission definition. Having the final goal described helps to have a discussion around the means to get to it.
Plus it can help to prioritize key efforts and to triage all the various ideas / enhancement proposals etc.
I know there is GitHub - jenkinsci/jenkinsfile-runner: A command line tool to run Jenkinsfile as a function section. To mee it feels too high level, I would like to see a more detailed description of use-cases so that people coming to the project can get quick info about where to use it, what it can help with etc.
As @rsvoboda mentioned in https://community.jenkins.io/t/jenkinsfile-runner-roadmap-discussion/583/3?u=oleg-nenashev, it would be nice to have explicit manifesto / mission for the project