You're basically doing the same then - comparing two numbers. It's just less flexible since it affects only hull mod and not specific ships - in other word ALL carriers would have 30 OP hangars except converted ones (so still no difference in what can be carried between a small support carrier and a huge carrier). To do that you'd still need a variable tied to a specific ships.
Why would the OP limit be global? The 30 OP example was for the largest bay on the largest carrier, not a value for all carriers. A fighter size system is unnecessary. A hanger size system limited by OP would achieve the same goal.
Alternatively, you could just make your superbombers built in and sidestep this whole problem. If you have different types of superbombers then you could have different ships and have a mechanic to switch between the ship versions at a station. Ironclads had a similar mechanic around 3 years ago.