LoadToadThe barbettes on the Me210 and 410 were purely defensive armament. It would be far easier to attack a target using the forward facing guns that were thoughtfully provided by the designers rather than attempt to get into a position to use the rear facing barbettes.
Kitbag I don't think the FW 189 with it's little 465hp Argus engines and a top speed of 217mph would have been much use as a night fighter. They did attempt to make a single seat ground attack version called the FW189C though. I don't think it got much further than the prototype stage as the Ju87G was a much more effective machine with it's two 37mm cannon which gave it the nickname Panzerknacker (tankbuster).