Fieldmouse you have a good idea but chances are a cruiseline has tried it, that came back to haunt them so no more.
I can imangine the CM gripe "I lost track of time and was 30 minutes late and the CL charged me 150.00 I mean I mean I could see maybe a 25.00 late fee but this is horrible." Well I will make their life miserable and will let 1000 people know never to use this cruiseline again.
People don't take responsibility for their part of travel as a TA I hear this all the time. Your website changed my reservation. "No you made it for the wrong date because you were not paying attention to what you were doing so now you have to pay to change it." The airline wouldn't let me board the plane because they said I was drunk, "Well then you shouldn't of been drinking." The airline shut the gate, now I am going to miss my flight and not make it to the cruise on time or go over to XX airline and have to pay 300.00 more that what I paid for the original ticket. "Then why didn't you get there 1 1/2 hrs. prior to departure." This is the best one. I am flying out of New York or Chicago in the middle of December or January, now the flight has been canceled and I will miss most of my cruise what can you do? "Well you could of flown out the day before or bought the CL air but you didn't so no this is on you. Lets us not forget the person that didn't buy the insurance and now has a illness and can't go so the cruiseline should make an exception. That is what the insurance is for.