With regards to altitude modeling, the battle was from my understanding played out between 4-6k and of the German bombers at least the Do-17 and 111 had service ceilings of only 6k, the Ju88 was the only one with a higher ceiling but even that was with no load!
The beaufighter would make a good addition to the RAF as a flyable, definately capable as a multi role job, and would make a good counterpart to the 110C-7
Maybe a Beaufort would be a good addition. Give em a HP Heyford or Harrow, that would be good for a laugh
Craig