Commercial pilot here, while possible (almost everything is possible at this moment), I don´t think it was a suicide, they even say at the article that if this is a suicide it´s inconsistent with previous cases where the pilot just pushed the controls and dived to the ground.
Why it´s too complicated?:

-To kill everybody via hypoxia you don´t need to climb to Flight Level 450 (45k feet). FL350 works just as good, the difference in the time of useful consciousness is 10 to 15 secs (from 35' at 350 to 15' at 450), not worth the trouble of climbing and possibly stalling the plane. After that time you either pass out or you start not knowing what you are doing.

-You don´t need to turn and fly for 6+ hours to random points, just keep your flight plan and selected altitude and the airplane will behave like the Helios (flying till the end of the flight plan and then holding till running out of fuel)

-Why flying for 6 hours if you want to suicide? passenger oxygen only works 15 min (time enough to reach a breathable altitude), the portable oxygen tanks for the auxiliary crew will work for 30 min more or less.. Look at this video of hypoxia test at 25k feet to see how fast you pass out http://youtu.be/hSrGfElyfVE

-why disconnect the communications? you only need to ignore them. why bother with the ACARS?

So far all the things are more consistent with a hijacking done by someone with some knowledge of flying a plane (like asking pilots to shut down coms, climbing descending, turning, introducing a waypoint), but not enough to know that flying at FL450 it´s so unstable for a plane like this, or that you´ll eventually will run out of fuel.

Also I must say that all theories are taking in to account good and skilled pilots and rational decisions at the cockpit (maybe from the hijacker). The captain really seems to be a skilled professional, but I don´t know about the flight officer. Friends of mine who are flying at Asian companies complain all the time how awful the instruction and flying skills are there. For example the pilots of the Asiana that crashed at SF just lacked basic flight skills, like using the thrust levers to do a normal landing. At china the flight officers are NOT allowed to take off, land or touch the controls below 1000' (How can you be a pilot without knowing how to land?, what happens if the captain has a heart stroke?). But I don´t know how good it´s pilot instruction at Malaysia Airlines.

I´ve seen very strange results during simulators when trying to solve emergencies, and all where very capable pilots. After all airplanes are very complex systems working in very different scenarios. Corrected procedures and system fixes are constant even on models that have been flying for 20+ years.

What I mean is that yet another possibility, is that the weird behavior is caused by some kind of emergency that went wrong somehow while trying to fix it, maybe due to a momentary bad decision that made everything more difficult, or just plain incompetence.

Also you can not trust all the theories and data they are releasing, it might be a bad interpretation, or just plainly wrong. For example, look at the Malaysian government, they told everybody that they lost track of the flight at one point. Everybody supposed that it was the actual point where they lost ALL contact (primary, secondary and acars), but it was just the secondary radar...and it took them almost a week to realize this. As this point is the ABC of Search and Rescue knowledge, I can not even imaging how many things they are screwing during this search..

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