I think this is a valid wish because it is very much true in AH that bombers drop ordnance at much faster speeds than they did in WWII. There are a number of liberties that HTC has taken in the name of game play (burn rate, map sises, etc) to help facilitate player interaction and to keep things in scale. Also, there is no wind and cloud obstruction is minimal with mostly non-existent.
With all that in mind, about the only thing I can suggest would be to not allow bombers to drop above X speed (say 260 TAS). But, the monkey wrench in all this is the speed in which the B29 must travel in order to stay in level flight which is above 300 TAS when it is loaded down with 20,000 worth of ordnance and full or nearly full fuel tanks. I know for a fact that my grandfather's B24D bombing runs were all done in the low 200's TAS, most of the drop's were below 8,000 ft, and he never saw 1000 lb bombs (most runs were done w 250 lb bombs). Granted, in the Solomon Islands of the South Pacific they were not worried about massive batteries of 88's and hordes of enemy fighters, they were more worried about weather, navigation, and range. Anyhow, I don't think a penalty can be applied to a flight of bombers but rather a restriction placed on the speed in which level bombing typically occurred. I bet HTC could "coed" in a limited on the bomb button. Thing is though how would they apply it across the board or on a per bomber basis?
This is one of those things to "be careful for what you wish for".