All that restricting alcohol, indeed enforing an alcohol ban, on board the aircraft is likely to achieve is to persuade passengers to, perhaps, get plastered in the airport bar before boarding!
But, as this thread was about, it's about an airline(s) offering a quality of service that persuades passengers to travel with them again and, in this respect, I have my preferences of airlines that operate from BHX, particulary Swiss and SAS. Based on my mentioned incidents with LH and KLM dissuades me from opting for them in preference to others so let them restrict alcohol, ban alcohol, adopt their attitude problems because passengers will vote with their bookings as they did when KLM banned alcohol.