re: the Iranians on board
http://time.com/20592/mh370-nourmohammadi-iran-malaysia/
Sure, as Time goes the article is a little overdramatized but ASSUMING Time isn't posting a bunch of fabricated bollocks the stuff on his facebook page for example makes it really hard to think the two of them would hijack a plane. And the investigators would have jumped all over it if the leads had gone anywhere.
Shady, yes. Sinister, no, not getting that vibe.
This really is a situation where the easiest/most obvious answer isn't actually the solution. Or, at least, the easiest/most obvious answer according to currently available data.