.... and speed should be THEE factor in adding or not adding a plane??? 
No. The Ju188A gives the Luftwaffe a mid-war bomber, something it lacks now. It is a bigger gap than giving the Luftwaffe a second early war bomber.
The Ju188 is better armed and faster, improving the two weakest aspects of the Ju88. That would make it useful in both mid-war settings as well as the MAs.
Certainly the He111 has a valid place in AH, but unless bombers are forced to fly at historical throttle settings, the Brits will continue to get slaughtered in the Battle of Britain setting in AH. The He111 is not a magical panacea that fixes the fact that bombers are flying at 260-280mph when they should be flying at 180-200mph.