It would be great for realism if there was a checkbox in the airline settings to charge extra passenger fees (checked bags, carry-on bags, maybe in the future ticket change fees).
It could be optional for your airline to collect those fees or not. For an airline that charges fees, there could be minimal LF penalty. So, it would be to the airline's discretion to decide what would help in the long run.
It would be great to have for fuel spikes or whatever event may come up. Well that's my two cents for today