The Defiant turret did rotate 360° and could be used in a forward firing position.
The fairings fore-and-aft of the turret were pneumatically operated and dropped
down as the guns rotated by. However, the pilot had no firing control, so even
when faced forward the gunner was in control. So perhaps giving him a firing button
would be a start.
Wing guns were mocked up on one turret-less airframe as part of a proposal for a quickie
single-seat fighter conversion during the BoB, it had two .303 per wing. A single 20mm
was also tested, the original French turret design had been for a 20mm gun, but major
aerodynamic problems were encountered. Replacing the four .303 Brownings with two .50
Brownings isn't as straightforward as it seems, total weapon weight is different with one .50
weighing about as much as three .303, and the forces operating on the turret mechanism and
structure are far greater, which would lead to an increase in weight, which leads to the requirement
for a more powerful hydraulic system which increases weight etc, etc.
Defiant N1550 was converted as prototype for the Defiant II and was fitted with the Merlin XX,
speed improvements were minor, seven Mk.1 were converted on the line to Mk.II standard
and a further 210 Mk.II were built new. Externally the Mk.II looked little different, with minor
changes to the cowling, slightly deepened radiator bath and slightly enlarged rudder.
Mk. I prototype with turret forward.