VRay & Corona have different philosophies. One's is feature richness & maneuverability while other's is fast turnaround & simplicity (ease of use).
Same from my PoV.
I oppose this extra option in settings, since it can fairly easy cause confusion & frustration with new users - if accidentally is turned off or never activated in the first place. For unaware beginner it could take minutes or hours to solve (mainly because of time to search, communicate, get feedback).
Second, IMHO, self discipline - better organization of the scene goes a long way and is strongly advised, to at least adapt faster to client's feedback (corrections & changes).
i.e. Use Layer system to organize Materials:
1 - Standard
2 - Displaced (Select all materials on this Layer, then deactivate Displacement on all. Done in one go!)
PS. Even, if you're not organized, selecting & deactivating Displacement (as proposed by beanz) will have no influence on materials not using it. Also, takes artists almost same amount of time to do either - deactivate in settings or on all materials.
PPS
Next thing will be caustics, hair, reflections... instead of learning, using passes, post-pro ;)