It's probably a limitation of the ordnance system in game, which is the reason why we don't have a lot of ordnance load outs that were historically used during the war.
ack-ack
6 (or 7?) options per column I believe. It looks like HTC has the ordnance options sorted between wings, bomb bay, and gun/ord packages (110G-2, Me 410). Or, any combo as needed as long as it is relative to the limitations of the load out (Me 410 = 50mm gun OR bombs).
The other thing we have to keep in mind is that I'm sure HTC will put in the more common bomb load outs but they also have to take in to consideration which options will and will not be used in the MA. Who would use the 4000 cookie and 50/50 lb bombs vs the 4000 lb bomb and a mix of 500 or 1000 lb bombs? Remember, there are only a certainly number of option slots.