Thanks for the clarification.
Based on your clarification, could you provide a few examples of the transformed Relay graph? It would be even better if you could include an example of mixing BYOC and graph pipeline, so that the discussion could be based on the example and could be more efficient.
Also, of course you could allow users to bring their own graph scheduler (a.k.a. runtime), but if we want to have this feature in the upstream, it would be better to have corresponding runtime support by default to make sure this feature is self-contained.
Finally, again please provide the complete upstream plan, including all the PRs you plan to file and their functions. It’s hard to review a single PR without knowing the whole picture.