I like this idea.
The way that WWII bombers had multiple bombs and im talkin the smaller bombers like SBD's
and Stukas that they would have 1 larger size bomb mounted under the Fuselage and smaller
bombs mounter under the wing. Their was also the option to either drop all at once or
drop them seperate.
For this case of multiple bombing runs in a single sortie have it so the larger bomb is
dropped first and does more damage, then when the smaller bombs are dropped it does less
damage that the larger bomb.
note picture of Ju 87 Stuka