That would be able to carry maybe four dismounts at the absolute max. A turret doesn't stop at the roof line, underneath it there is a turret basket with a clearance area around it, if you look at any APC the actual troop compartment generally starts a bit back from turret ring and physics hasn't changed that much since WW2. If you want an APC as opposed to an IFV then persuade any of the powers that air bursting artillery is a big enough danger to warrant the extra cost, weight and loss of visibility. If you want an IFV then you need something like a much longer and more mechanised Spanish Civil War to convince armies of the desirability of such a vehicle.
Inside of a Warrior IFV as an example.