The evidence that the pilots were deliberately masking their flight path shortly before the flight's disappearance, was pretty compelling. I've always felt that the plane was intentionally maneuvered somewhere, but clearly the destination was not dry land.
So we assume for a moment that some organized group deliberately did something to this aircraft. Who has the motivation to execute such a scheme?
Government agencies I rule out - because of lack of a cover story. It does a government no good to leave a massive mystery open to the court of press speculation, especially for so long. It grows distrust in the populace and gives the perception of incompetence, which undermines power. Plus the political risks of being uncovered are too great. There needs to be a cover.
I'd rule out corporations or business moguls for the same reason - leaving mysterious loose ends is not in their best interest. Too much risk to reputation.
Terrorists I rule out as well - they are motivated by public gestures that further the cause. They'd have claimed it immediately and even if the plot was steal the plane and use it later, they'd have done it already.
So what nefarious organization is left? What group would be OK with leaving a mysterious unsolved disappearance out in the open? Criminal syndicates.
Professional criminals are in the business of doing bad things and getting away with it without a trace. To a career criminal, an unsolved mystery is a point of pride.
If there was someone or something of extremely high value aboard the plane, perhaps being smuggled, organized criminals would have the motivation to extract it, far away from law enforcement or even satellites, and bury the evidence without a trace.
But they would have a difficult time landing an aircraft of that size anywhere on land without detection. Eventually it would turn up.
So how about on water? Ditch the plane gently on the ocean, Captain Sully style, extract whatever is in the cabin and then let it sink slowly. Disappears without a trace. Do it far enough away from civilization and nobody will find it.
Pretty elaborate heist, and absurdly risky. But criminals aren't known for being overly risk averse. And even if they botched the job, we'd never know about it.
So that's my theory over who would be responsible. Definitely backed up by what you're saying about the level of organized crime in the Malaysian political world.
That plane was carrying some person or thing that a highly corrupt, well financed individual or group wanted very badly - either to take for themselves or destroy. And so far, they've gotten away with it.