I think we get ourselves into a tailspin when we try to figure out some fair way to explain how God must treat everybody. We overlook the simplicity of what you have suggested because we are afraid of the implications of having received grace. We don't have to explain or to come up with a rational teaching to explain how all of the individuals in the world seem to be getting treated unfairly. We just don't really know an awful lot of things and we get ourselves confused when we worry about explaining the IMPLICATIONS.
Grace is undeserved. Always has been, always will be. Our desire to come up with a way to answer everybody's objection to it (including yours and mine) only causes us to miss its vastness! Sure, some of the answers have some value to them, but it is not really those answers that are the problem ... it is our PERCEIVED need to justify the fact that WE have received this grace when so many others reject it. Not only do I NOT have an answer for that ... I don't NEED an answer for that. Our lack of an answer forces us to recognize the miraculousness of the fact that we actually believe Him when everything that is of the world screams out that we are fools for it.