I think technically Kakashi has an EMS eye. He just doesn't have the chakra to even come close to using it effectively. To have an eternal sharingan eye, you don't need four eyes, you just need a "2nd" eye or a second activated sharingan eye transplanted in place of your original eye. So because of this I don't think it's possible for him to lose light.
Like when he died during the pein fight, I don't remember too well so don't quote me on this but I think he lost consciousness, he didn't lose his light in his eye. And I don't think his sharingan ever deactivated. If I am remembering correct, that would mean that he does have EMS. Because a regular sharingan user's eyes actually deactivate when their chakra runs too low, so if Kakashi was running low on chakra, his eye would've deactivated before he died. But this isn't proven so Idk :shrug: