Thanks for all your responses.
This thread was really motivated by upgrading out test infrastructure to use es8 and this thread is related to NPE Initializing PluginsService in ES8 - #3 by buitcj in that our test infra was relying embedded mode. If embedded mode is no longer supported then we don't need to have the es8 server libraries in the same process, and there shouldn't be a library conflict anymore. This now makes sense to me.