I am really interested in the reasoning behind the hull mounted gun, as said - I was thinking initially the same line of thoughts.
I confess I would have gone for the hull casemate myself, mainly for the "historical" reason that the turret and the turret ring wuld have been too small to accommodate a large gun (historic precedent e.g. the original B1, the M3 "Lee/Grant", and an early Churchill, IIRC).
Also, for purely aesthetic reasons (the apparatus could be rather compact on the inside, for what it is worth), the proportions on the model look just a bit off. A slightly smaller antenna might have fitted the turret better. The overall execution and painting is beyond reproach, as usual.