Not a bad theory. Though in my honest and most likely correct opinion. It was Hiruzen who let Itachi borrow those weapons. It was all part of Hiruzen's great plan for the Eternal Hype Project. He needed to make sure Itachi played his critical role in all this, and therefore gave him the Yata and Totsuka. Believe in the Hype! (Hiruzen 5 Leggo)
So, basically Obito was using Itachi, when he knew that he would never complete his one mission to capture Naruto? And that Itachi helped only with sealing the jins? He was okay with Itachi doing the bare minimum, was cautious of him, and didn't touch Konoha for the 7 years that Itachi was in Akatsuki. That's not using someone. Any other missing-nin could have done Itachi's job. Someone else would have been for Akatsuki and they would have captured Naruto long ago. Itachi was more of a liability to the organization than help, Obito would have been better off killing him if he were interested in using someone and benefitting his plans.
ot:
-Obito didn't know everything in Itachi's arsenal (just as Itachi didn't know everything in his) and asked Zetsu to show him the recording of the fight afterwards. When Itachi stated that Obito trained him, it was just to give an excuse as to how he knew Obito and cause Sasuke to be weary of him.
-Obito has no reason to give spiritual weapons that have practically no limits on their own to his enemy.
-Both black zetsu and white zetsu were completely surprised that Itachi had them. They inform Obito of everything. Obito had no idea that Itachi had those weapons.
-Itachi has been researching things concerning the shinobi world since he was 7...if anyone was going to find those weapons at that time other than Orochimaru, it may as well have been him. The manga also implies that he found them himself, considering that Orochimaru was like "Itachi...these were with you all along" and BZ stated that Itachi found them before Oro did. The point is that there are absolutely no hints as to anyone giving them to him.
It's not that hard to believe that a 13 year old prodigy found them. Especially considering Itachi's track record and tendency to do things no one his age should be doing and at such an early age.
-He saw war and was in a battlefield at the age of 4.
-He cared for the village and read ancient texts at the age of 7.
-He graduated from the academy at the age of 8...one year after entering it when the usual time to graduate is 6 years.
-He became a chunnin in 6 months after turning 10.
-He was a double spy since the age of 10.
- He joined Anbu at the age of 10 in the manga. What 10 year old boy joins a tactics/assasination squad?
-He became an Anbu captain at the age of 13.
-He took on an S-Rank mission at age 13.
-He became a missing-nin and murdered his clan to protect a village and the clan's own honor at age 13.
-He beat hokage level opponents as a 14 year old (Orochimaru)
-He beat other missing-nins at age 17 (Deidara) and others
-He stopped Edo Tensei at age 21...while an Edo.
Look at that. Most of the things he did were when he was younger. Why is it so hard that a kid like that would find Yata and Totsuka? If you compare him to the other people that were alive in the Naruverse at the time...it truly is not.
Also, considering that Yata and Totsuka were being searched for by Orochimaru, one doesn't need a susanno to utilize them. So Itachi could have found them prior to even awakening susanno but decided to attach them to it once he did.
However, I still appreciate the effort you put into this thread and it truly was an interesting read.
Obito was little scared of Itachi, it was confirmed when he said "Itachi is finaly dead, now Konoha is not off limits any more". Don't really see the reason to give these powerful items to enemy who are very powerful.
It's the same as Orochimaru mentoring Sasuke. There's barely any difference between the two situations. Orochimaru was preparing Sasuke to be his host and Obito was developing Itachi's ocular powers for Sasuke.