The ultimate Beaufort proposal appears to have been the so called Mk.IV. This would have incorporated the Taurus XX with 1,250hp, a two-speed blower and fully feathering propeller. The Merlin XX powered variant would have been the Mk.III. In addition to the new engines the dorsal turret would have been a four gun version apparently designated the B.XV. Supposedly one Beaufort (AW372) was converted to that standard. There was also an experimental twin .303 browning nose mounting (separate from the under defence mounting and the gimballed Vickers K-guns) tested but never adopted.
The B.XV turret is interesting as the only other reference I have ever found to it says it was installed in the Beaufighter V (only two aircraft, R2274 and R2306) yet these were actually equipped with Boulton Paul Type A so there seems to be some confusion around this turret.
Finally, when it came to producing a Beaufort replacement the ministry preference was for a Beaufort fuselage with Hercules engines and Beaufighter wings, it was Bristol's that suggested external carriage of a torpedo on what was previously a long range fighter. No Bristol Type number seems to have been assigned to a Hercules powered Beaufort so the idea probably didn't get much beyond the suggestion phase.
As for solid noses, don't forget the 12 x .303 Martin Baker nose developed for the Havoc Night Fighter.