So armor thats sneaky as Light but not as much, and armor thats as endurable as Heavy but not that much... no.
Pick or the other and get used to the pros and cons of each but dont make Meduim Armor. Hell I dont even know how that will even work.
I could easily get used to one or the other. I have already- I played oblivion. Medium armor would work in that its a happy medium between the two, suitable for a jack-of-all-trades kind of character, of which I know there will be many, as there were many in oblivion. Medium armor allows someone to be a finesse warrior who doesn't have to be a meathead standing in absorbing all the punishment- instead they could dodge block or parry their enemy's blows. It also allows for an archer who can more easily transition to a melee role and not have to worry overmuch about their light armor ripping to shreds. Like I said, this should be all about choice. Just because you are being somewhat narrow minded doesn't mean this idea should be totally scrapped.