No single approach will solve security issues on board airliners. You need a multi-facet approach:
1. Improve security at the gate lounge. Better scanning and detection.
2. Redesign the airliner. Self contained cockpit with washroom and galley. No door into the cabin - just an impregnable bulkhead. Fit an external door for crew access.
3. CCTV and electronics to monitor systems and cabin.
4. Marshals on-board - armed.
5. International terrorism should be declared an act of war. No civil trial and years languishing on death row - a simple court martial and death by firing squad!
Don't arm the crew - you have you read some of the posts by pilots on this BB. Could you honestly trust some of these jackasses with a side-arm, in a pressurised cabin with a lot of people?