The first problem I have with this theory (Turkey) over the revenge killing theory (al-Libi) is that why would AQ telegraph it for weeks or even months (chatter + Stevens "need security force" emails).
al-Zawahiri wanted revenge for al-Libi -- and remember al-Libi was a terrorist who specialized in attacking embassies! -- and so they get the "Rahman Brigades" to do it as almost a cut-out, instead of AQSL->LIFG, who you would have expected as the first stringers if it had been a Turk-related arms deal gone bad.
The second problem I have with this theory is that I fully expect Bobo to try and tangle up this whole investigation by flooding the zone with various ideas of inestimable internecine warfare -- remember, they blamed the whole thing on the tape, then Romney -- rather than the truth; and the arms deal lends itself to that kind of palace intrigue, versus the hard-copy truth of the Embassy missives imploring State for enhanced protection, and the subsequent consequences of State's negligence.
Benghazi
We have a history of presidential second terms that explode in a scandal lingering from the first (e.g., Watergate) or due to hubris (cf. Reagan’s with Iran-Contra, or Clinton’s with Monica) deteriorating into scandal or just fizzling out (Bush and Katrina/the Iraqi insurgency). I used to think that the Libyan crime (not beefing up security when earlier requested, not immediately sending over help from the annex, not sending in relief during the various seven hours of assaults, etc.) was dwarfed by the cover-up (by all means protect the administration narrative of Libya as success/al Qaeda as impotent/Arab Spring as wonderful/the slayer of bin Laden as cool and competent commander in chief).
Now I am not so sure. Why did we even have a consulate in a secondary port city, when most countries had pulled their embassies out of Tripoli? Why, on the night of his death, was our ambassador meeting with a Turkish diplomat in Benghazi? Who delayed our team at the airport — and why? Why was an annex, with a large CIA contingent, even nearby? Why did the annex people apparently want to keep a firewall between themselves and the consulate? Who actually were the terrorists? Who paid them and what exactly was their mission? Were we destroying the Gaddafi arsenal, or rounding it up for anonymous resale? And if so — to whom?
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Here are some thoughts by VDH over at PJM. Some really good questions which I think he already has the answers to as well.
Well, you know far more than I on this topic but we know the Turkish Consul General Ali Sait Akin had met with Stevens 40 minutes before the attack. I believe he gave the green light for the attack. Something was known in advance regarding a major fraud (regarding weapons bartering) perpetrated on the terrorists by the U.S. That there was also possibly a prison at or near the annex.. Perhaps Akin wanted someone released and gave go ahead for attack? In any case, it all boils down to 0bama not wanting to shame his BEST BFF foreign leader friend, the President of Turkey, Prime Minister Recep Tayyip Erdogan.