The thread asks, "How far can they go?" My guess is, "Until someone dies, or is so seriously ill in hospital that it cannot be kept out of the papers."
I am not making any quesses as to how this might come about but base the prediction on the well established history that mankind allows a difficult situation to 'slide' until it become a dangerous one and then allows it to 'slide' again until it falls off the edge and breaks.
For example,the ship Herald of Free Enterprise in 1987 and various sports stadium disasters, all of which could have been averted and where acountable mistakes were made. Often with specific warnings ignored - such as the London Kings Cross tube disaster (also 1987).
In conventional commercial life, it is still cheaper to wait for a disaster and then repair it and pay compensation. For airlines it can be differrent. If someone dies onbaord from alcohol poisoning, then the carrier is not going to suffer too much and will continue to carry the groups - albeit with a little bit more warning. That means, ensuring that all blame is minimised!
As the drunken group cannot access the flight deck, they ought not to be able to endanger the hull and, for as long as that continues to be the case, the airlines will take the bookings.
Cynical? No, just based on 48 years of observing the human race!
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"I tell you, we are here on Earth to fart around, and don't let anybody tell you any different." Kurt Vonnegut, Jr.