The Mossie is a fighter, not an attack aircraft, and carries far less than the A-20 let alone the A-26. The A-26 is faster than the A-20 and carries half again, or more, than the A-20. Its comparative lack of agility is irrelevant as it is an attack aircraft, not a fighter. The reason it will be perked is that it would be too dominant in its role if it were free. It is likely to be the bottom end perk bomber with a cost of 5-10 or so perks.
Well, on an A-26b (Early) it carried 6x 50s in the nose, A-26B carried 8x 50s in the nose.
Optional Gun packages are this:
2x .50 cals and a 75mm Cannon
4x .50 cals and a 37mm cannon
2x .50 cals and a 37mm cannon
75mm cannon and a 37mm cannon
2x 37mm cannons
The Gun pods under the wings now, carry 4x .50 cals under the wings, however late production A-26B's carried 3x .50cals per wing (removes the gunpods which degraded performance)
Top that with 6,000lbs of Ords and from 16x to 18 .50cal machine guns.
There are glass nose B-26s used for level bombing, you simply lose the nose mounted and gain the wing mounted machine guns for forward armament.
So in retrospect, it will easily be perked, most likely something between 20 and 50 perks.
From what I see, A-26s served in action during Battle of the Bulge, the Pacific and Italy.
Pacific service - it was in the philippines, pretty late action, overall I can say it served quite a few full squadrons in combat action.