LOL! You need to think more and evaluate your criticisms before you make them. Refresh yourself on the character's wikipedia page or something.
There is EVERY reason for Tuco to be involved in the story for exactly the reasons you (cluelessly?) say that he shouldn't. Breaking Bad established that Mike also worked for Gus/the Salamanca Cartel and Saul was involved enough to be aware of Gus. He had to become involved with them SOMEHOW, and this is how. Did you forget that Tuco was a Salamanca, just like Hector and the Mexican Murder Twins?
I know you want your criticisms to be valid, but you incorrectly concluded that it's a retcon. The fact is that Breaking Bad set up Point B for Saul's back story. That is where he has to get involved with Gus and the Salamanca Cartel in some way enough to know about them when he helps Walt contact them through Mike. Point A would be far less interesting if it weren't set before this involvement began. To ignore that potential would be idiocy. It's a simple Point A to established Point B story at this point. By definition, it is not a "retcon."
Sorry, but I'm very glad someone like you isn't directing this show's writers. :awe:
Uhh, Gus was already Mike's primary boss when we were first introduced to him. There is no evidence that he ever worked for Saul first. So far there have been subtle signs that Mike may already be involved with Gus and/or the Salamanca Cartel in BCS.
There's an obvious elephant in the room you seem to be ignoring: SALAMANCA! Tuco is A SALAMANCA! Gus and Mike controlled territorial distribution for and even directed THE SALAMANCAS! Gus eventually overthrew THE SALAMANCAS. For Saul to set up Walt and Gus through Mike, he had to be previously involved in something at least enough to be aware. A brush with THE SALAMANCAS is the perfect way to reach the scenario setup by Breaking Bad.
BB's scenario is just BURSTING with potential, and you expect them to ignore it?! While it may be low-hanging fruit (often the best/most-realistic kind), this is the exact opposite of "forced." This is one place where that complaint is demonstrably, provably, WRONG. It's not even an opinion.