His sharingan cant be turned off like an EMS and who said he can't deactivate it because he is not uchiha? where in the magna does it say that?
well it is common sense if you understand how the sharingan works.
The sharingan is activated when uchiha blood circulates the blood vessels of the eye, thus activating it.
Kakashi is able to use sharingan becuase the blood is always been circulated inside the eye, even when covered up. If he finds a way to deactivate it he will loose it permanently, because the blood will just coagulate and his eye will loose light.
He is able to use MS because he overuses the blood inside the eye, but the exertion of the blood causes him extreme fatigue.
He is not able to use EMS because it is necessary to have a related uchiha blood in the company of the eye.
(This is medically speaking, but it may be incorrect. just don't bash, is an anime anyway, if he has MS or EMS will not impact are life)