27 Mk XVIII's were built. Yes, a very low number, but they saw heavy use, sinking many ships and U-boats. Not exactly historically insignificant. Much more significant than the Ta152 as a matter of fact.
Cobia,
I have nothing against new versions of the A-20, presuming that the new version is not a rare cannon armed version which would entirely replace the historical 50 cal armed A-20G in use in AH. You're request for the cannon armed A-20G had nothing to do with the historical use of the airplane and everything to do with "get me four cannons!!!!!!!"