I would get very worried about passengers being willing to "lend a hand". All you are likely to end up with is a free-for-all, and the end result of that is the incident where a passenger was killed, allegedly by another passenger jumping on him from the adjacent seat.
My company has been assessing a fairly impressive passenger restraint device, which flaps' company has also been looking at. Using it, effectively solo, in trials, a 5' girl managed to restrain, and put on the deck, a 6' square ex-marine.
When we looked at it, I played the part of a disruptive passenger, and I was fighting HARD. To no avail. It safely restrains people really quite nicely. I would much prefer to use that than have to ask assistance from another passenger who, let's face it, may either be gagging to punch the guy's lights out, quite possibly putting the airline in court, or he may be his mate, and playing along until he can punch out the hostie.
Even if this helpful soul is a genuinely helpful passenger, the chances that they are at all trained in what they are about to do are slim, whereas the cabin crew are (hopefully) well-trained in calming techniques and restraint as needed.
Re pax smuggling their own booze on board, I would make it an international offence to do so, penalty to be decided, but sufficiently draconian to deter offenders. It is, after all, a flammable liquid, and we don't allow them to have even small cans of lighter fluid, so why a whole litre of overproof vodka?
Another device that is sorely needed is an IATA-run blacklist of disruptive passengers, with details available to airport check-in staff, travel agents and airline booking agents. Alternatively, or in addition, on conviction their passport should be surrendered for a period set by the court. And before I hear comments about domestic flights, I would make it a requirement to show passports for those as well.