I feel it is a bit harsh. One minute you can carry 4 engines, 4 turrets, waist guns and a minimum of 6k bombs. The next minute you are down to 1 turret, 2 engines and 3k ords in a B-25c, or 4.9k ords in a ju88. Also of course the ranges of the twin engine planes are generally more limited.
Wouldn't it be lovely to have B-17D with 3-4k max load, or B-24D or Halifax B3 Special with bombs or glider troops, or even something "completely" defenceless and useless like a FW200 or Stirling, but it has the range and load in between a B25c and a B-17G.
I know it's not likely to happen, but my only choice seems to be ju88 or Tu2 (fi you can get them) for a decent load.