There's a lot more that can be said...
1 - It is possible for the pilots to depressurise the fuselage AND disable the deployment of oxygen masks from the cockpit.
2 - Cockpit doors are heavily reinforced nowadays, so the pilots are safe from the passengers.
3 - The aircraft flew particularly high, and then particularly low shortly after contact was lost. This is consistent with an attempt to kill passengers rapidly from hypoxia and then re-pressurise the aircraft.
4 - The aircraft track seems to have altered several times after contact was lost. This is consistent with an attempt to match speed and height with Singapore Airlines flight 68. If flown closely, two aircraft become one radar blip. SA68 was on course across India and the Middle East.
5 - To the south, the Cocos Islands have a suitable airstrip, and only 600 inhabitants. This is sufficiently low for a small group of armed men to take it over.
6 - Though the only fatal accidents this type of aircraft has had to date have been pilot error, it has had one major cockpit fire while on the ground. Such a fire in the air could render the aircraft uncontrollable and cause all communications to be disrupted, but might not cause it to crash immediately.
7 - If you want to hide an airliner effectively there are very few ways:
a) put it in a row of many similar other airliners
b) crash it into dense jungle or deep snow
c) land it carefully on a deep part of the sea so that it does not break up, and let it sink intact.