@hvelarde as said many many times already, I don't get your point. Plone 5.2 ships with plone.restapi. If you want to use it, you should deploy it properly and make it available under "/api". You will have classic Plone and plone.restapi completely separated and there is no way in the world you can poison your cache.
I am happy to add a deployment best-practices section to the plone.restapi docs if that helps. We are using plone.restapi in production since its pre-alpha state and we never ran into that problem, because we always deploy it under /api and do not mix up things. The issue you are describing is super complex to solve, there is no general agreement what to do and the simple solution is just to follow best practices when it comes to deploying REST APIs.