First, my condolences to the families and friends of those who was made victims by these madmen.
I am not in favour of arming flightcrew, be it cockpit or cabin. The essence of my reservations is two-fold. Neither cockpit nor cabin are properly trained for this, and whats more we were not hired to be police officers. Being a police officer is a very demanding job under the best of circumstances, and I have nothing but respect for those who choose this walk of life. But I did not, and have no intention to do so.
There is also the training to be considered, not just gun practice, but the whole concept of being mentally prepared to put a bullet in another person. Finally, as many here have already mentioned, putting firearms onboard could serve as a means for hi-jackers to obtain control over weapons.
But it will be possible, on wide-body jets, to make the cabin a safer place by having doors replacing the curtains as cabin dividers. I do appreciate the practical problems with cabin crew needing to move back and forth. However, if each cabin was seperated from another any would-be terrorist group would have to be of substantial size to control all areas of the cabin. Would that serve as a deterrent, or does these groups have an infinate supply of members willing to die for their cause ? Would it be easier for airport security to spot these people if they were forced to show up in strength (say 8 to 10) ?
Physically seperating the cockpit from cabin would require radical rebuild of the fleets, and would not enhance the cockpit-cabin cooperation. Installing heavy doors might serve as a deterrent, but is it technically possible to design them with due regard to depressurization ?
But at the end of the day, if a hi-jacker is holding a knife to the throat of a cabin crew member, shouting through the intercom that he will kill him/her if the door is not opened what would reinforced doors help ? Would you be able to disregard a collegues screams and land the aircraft ? Maybe here on this board you'll "Yes" but what about real life ? Maybe a crew member you've known for years .. might be a friend even ... impossible odds.
I am convinced that this problem needs to be addressed on a political level at first, erasing these madmen from the face of the earth. And then work hard to create a political climate in their home countries, which does not drive young men into the arms of fanatical groupings. Probably Utopia ..