+1 but I don’t think this goes far enough 
I want to seriously suggest that for Sumac we aim to have an option to build+run Open edX with no frontend files in the edx-platform at all. As I mentioned in this post:
I commented out the 14 commands in Tutor’s openedx Dockerfile that are related to static assets or Node.js, and the time it takes for
tutor images build openedxdropped from 10 minutes to 30 seconds. And it runs fine, and works well with the MFEs - the main missing piece is that XBlocks cannot render in the learner MFE without the iframes/assets from the LMS. So it’s not quite usable yet. But, if we can solve that one thing (rendering XBlocks) and probably also implement the Instructor Dashboard in an MFE, then I think we can start to offer a “no legacy UI” build of Tutor Nightly that has all that stuff disabled and builds the platform much much faster.