It was more than just a gun package and merited a different variant number - mosquito XVIII 'tse tse'.
Tho mollins was an excellent armor penetrating cannon that was used as a groud weapon against armor in Africa, and had a naval version as well. All mossie XVIII were delivered to coastal command squadrons where they were mixed with mossie VI in anti shipping and anti sub work. While they were few in numbers they saw heavy usage and much action. They were also credited with a kill on a JU88 using the mollins and may have shot down a 190, but that it not verified. Shooting the mollins in A2A must have been awesome - it had about the same muzzle velocity as the hispano.
True, the mollins gun was a heavy beast, but then agan, it was installed insteaf of the 4 hisanos, so the net gain in weight was not as high as one may expect. The extra armor did icrease weight, but performance did not deteriorate by that much. In AH it will probably like flying the VI with internal bombs and a bit more fuel to simulate the extra weight.
I'd love to see the Mosquito XVIII in AH. Imagine the B25 with a hell of alot more performance, and an AP cannon that shoots about 1 round per second and it would still be a half decent a2a platform.