They were so heavily loaded down that once the other bombers dropped their bombs these planes fell behind and were preyed upon.
There's a reason they didn't get past the experimental stage (the "Y" means prototype).
Also, with the way bombers fly in AH, you already have this. Formations have more guns firing more accurately on any given target with much better range of defensive fire than any bomber historically had. They also fly at full speed with 1/4 fuel load, climbing many times better than historically possible, and flying nearly 2x as fast as historic cruising/combat speeds in most AH examples.
You already have AH bombers that fly faster, climb better, float gently at altitudes higher than they could historically reach, fire more defensive guns on attackers, with better defensive gun accuracy, and can drop bombs with laser accuracy from 35k without missing....
And you want more?
[edit: typo fix]