I went on eight crises last year alone, I am Elite with Celebrity and Princess.
No way in a blue moon will all the cruise lines enforce penalties against passengers, unless safety is a issue.
Celebrity has printed a policy and does on occasion remove personal items upon a complaint.
But it is short lived.
About the flashes in the Theater, with out enforcement, people will continue to use camera's.
Concerning extra staff or cost.
Cruise lines already have staff working the venues, they just do not enforce a warning system with penalties.
Yes, it will go against the grain of a few, but will gain loyalty with many.
About the dress code, I have seen on occasion enforcement, The passenger goes and changes or heads to the buffet.
Anyway, We can all agree that it is a ongoing problem.