I think it's a fantastic idea, it deserves its own discussion group elsewhere if this is really going to work.

My two cents for the game.

About the ontology of the game mechanics: a player has informations and sources of informations.

Informations have as property a degree of probability and are/must/can be linked to information source(s).

Information sources have as properties a set of failure modes, linked with their own probability, and can be linked to informations or other information sources.

In your example, the information is the assassination attempt, and the source is Bob. When you dig deeper, you find out that he has a source of information, Alice. When you question Alice, though, she tells you about not having spoken about an assassination, but just a big event. In this case, we have another information, just the big event, from Alice (another source of information). But they are competing, so which is the failure mode? Is Bob lying, or just fantasizing? Or the failure mode is Alice, which is downplaying the information she gave to Bob? Another example might be a computer, with hacking as it's failure mode. Maybe at a certain point, when you have constructed your neat probability network, you find out that all the root nodes have a failure mode connected to a single source (the classic conspiration plot), etc. With this model you can play a lot with the plot...