This seems like wishful thinking and inaccurate reading on the material. Gin was no double agent. First off for over 100 yrs from being a child before getting in good with Aizen he clearly with a sociopath just killing people in his way indiscriminately. Secondly It seems rightly out of character that Yamamoto would be in the know about Aizen prior to the end of the SS arc. Nobody knew anything about his activities let alone one of the closest people to him, Momo. Third there was no set match ups. if you can find anywhere in the source material where Yamamoto told people to go fight certain characters. Toshiro and Harribel have nothing in common but their abilities being similar in relation to water. Even then his is far more powerful and versatile. Shunsui and Stark have nothing in common besides the fact that they are both lazy. There background isnt the same, their abilities arent the same. It was also very clear that Nobody in the Gotei 13 was aware of the abilities of any of the arrancar that they fought. That information only came out in the battle. Thus proving Gin didnt release any information cause he wasnt on their side but more importantly even if he had said information would have been useless given the way the battles happened. The only Gotei 13 member with prior information on an arrancars abilities before fighting them was Mayuri who used spy cams placed on renji and uryu during their fight was Szayel.
Fourth of course the medallions didnt exist from the quincy when yamamoto first fought them. The who existence of them wasnt known until Chojiro died and even then they werent sure what it really did. We are supposed to believe Yamamoto was privy to all this information and didnt use it and also allowed his own bankai to be taken. They were countered until Urahara's intervention thus returning them to their owners. There is no basis for this line of thinking. By your logic he would have had to know about medallions he couldnt have known about, Because He would have to know the quincy were alive and thriving in the shadows of the seireitei. But more importantly the medallions work on whoever is activating bankai it has nothing to do with who revealed their bankai. Yamamoto had reveled his bankai in the story until that battle against Rloyd and it still got his bankai stolen, in fact given the little information yamamoto had on it he deduced wrong that his couldnt be taken cause the quincy cant steal the bankai's he didnt know that limitations of. Which seems to be the incorrect bases about how bankai are stolen. But more importantly What does Gin revealing some intel (he obviously didnt give) about his subordinates in the arrancar army have to do with a enemy that nobody knew anything about such as the Wandenreich quincy.
There is no complex character to Gin. He is a self serving sociopath that had the weakest reasoning for wanting to take out Aizen (Rangiku being hurt some 100yrs ago). Nobody knew that reasoning but him and even still it didnt justify any of the horrible things he did over the century. Plus his plan had to be the dumbest one since he knew the weakness of Aizen's shikai for many decades and only chose to use that knowledge when Aizen was at his most powerful and didnt need to rely on the tricks of his zanpakuto any longer. Gin of all people knew Aizen the best and was a child prodigy and a master of manipulation himself and still fell to arrogance. Its nice that he wanted to avenge his friend who might i add he turned his back on long ago but there is no justification for his actions. Even Rangiku was left puzzled by his actions. Also there is no correlation between him the fights that took place against the arrancar and most certainly not the Quincy.