My 2c's worth on the topic of the contents of the cargo manifest...
Given the total lack of information, the valuable cargo theory is at this stage not an entirely implausible one. BUT:
Having some experience in ground ops, I can safely say that high value shipments have some rather special security procedures, and information is circulated on a very limited need to know basis. In many cases even the shipper does not know which actual flight it will be on until airborne, and the crew does definitely not know in advance.
IF one would want to divert an entire T7 to get at the valuable cargo, that would need to involve some very sophisticated advance planning, and would need the crew as well as several other individuals high up in the decision making chain in the cargo and security areas as accomplices, not to mention the logistics at the other end. It is certainly not something any crew would be able to organize on impulse once seeing the cargo manifest.
Until cargo manifest is released I would call this scenario not impossible, but highly improbable.
Anyone heard of any official reaction on the claims of the WSJ article from any of the involved parties ? It is definitely not a claim to be taken lightly.