Here is a "tin foil" scenario.
1. He went to Iraq to help the dissidents.
2.He helped by using his technology knowledge to tap into military and/or private contractor communications.
3. The communications provided data to the insurgents that gave them a heads-up of comings and goings of military and contractor travels.
4. The advance knowledge of the routes and times of travel provide the insurgents with the ability to ambush contractors and military.
5. He returns home after setting up the links for the terrorists
6. Something makes the terrorists request his return to Iraq.
7. His return gets the curiosity up of the FBI who detains him with Iraqi help.
8. The FBI finds nothing but suspicions and attempts to convince him to go home.
9. Berg decides to finish his work for terrorists and declines safe passage.
10. Berg meets with terrorists who have decided he is has too dangerous information and is convinced to stage himself as a hostage. Copying other hostages.
11. The end.
And a tip of the old tinfoil hat to you, sir.
I'll say it again. This is beginning to look like the old Rosenberg family. Somebody knew too much and had no common sense.
I think your scenario makes much sense.
... the end ...
You have come up with the mother of all conspiracy outlines.
Strangely, it fits with much of what we know. As I've said before, the one thing that has to be debunked is that this guy was honestly, and even privately, "proBush"...