Boston with Torps? +1 - although I think there would need to be a tweak in the speed for a successful launch of a torp, because I don't know how I would get slow enough for a successful torp launch.
Quad 20mm option? Sure, why not. It probably had about the same usage as the 50mm in a 410, and it would have its uses. 60rpg is a bit light, but you would get one really nice strafing run before you died.