Theoretically, since there's little evidence that the aircraft ever flew with any armament, and a survey found that the Defiant could only have had 4 forward-firing .303" Brownings fitted, so a completely new wing looked likely.
It's also a moot point if 12 "pop-guns" constitute "more heavily armed" than 8, since, before the war, the Air Ministry had set its sights on cannon armament, with the first cannon-armed Spitfire flying in 1939, and plans for cannon-armed Hurricanes at the same time. 1940 showed that the .303" was becoming less and less effective against German bombers, with their increased armour, and was equally useless against the new breed of fighter.
It was only useful as a back-up to the cannon, in the event of a deflection shot, when the weight of fire gave an even chance of hitting the pilot.
The Defiant was viewed as a bomber-destroyer, and its "set piece" attacks were all set out against bombers, with fire being delivered from the side, or the front, where armour was less effective. It was never anticipated that it would have to cope with faster fighters.