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.