Hi Matt
I noticed someone made a similar question on the github I had regarding the OWTF project.
Just as suggestion, as I know you are building a tool from scratch in Ruby.
Agree that the focus of OWTF is pen testing and Pipeline is broader as it could be integrated with SAST tools from the build process. I would have expected here FxCop (.NET)as is really a tool that is already integrated into VS studio and the results could be extracted into a 'Pipeline' during the code. Also OWASP O2 can serve you for this purpose as SAST tool.
Checkmarks & other vendor tools are quite expensive but I see the utility of having an open source tool integrating with Commercial tools, however from my open source perspective I think that integrating with first SAST/DAST open source tools makes the use of the Pipeline open to everyone. Right now potential users of this tool are limited to vendor tools with exception of Threath Fix which is also open source available.
If I understood well, the purpose of Pipeline is to be integrate it into the build process, therefore I think that adapting OWTF to integrate with the build process is question of building a module to do this. The one thing missing into OWTF is a module into the first pipeline process in code, m SAST module . In this case open source tools like FindBugs or FxCode will be by first priority.