Does he need to, though? Not trying to play Devil's advocate here and I don't know how much data or information is out there but it seems - to me - that saving his legs and less running, etc, in a corner spot might make him a better offensive weapon.
Now, if the Brewers feel he can handle CF and they find a corner OF bat that is strictly a corner OF (like Yelich) then I can see that move. But for now, I feel like's fine in a corner spot.