I feel very similarly, 7even. I think that's why many fans like myself won't hold it against the player if he were to leave. If it were me? Obviously, I'd fight for my place at the club I love but Thiago has been quoted before as saying his dream isn't necessarily to succeed at Barcelona but to succeed in football. I always took that to mean, he aspires to greatness, irrespective of the shirt. I think the Cesc thing has to hit him personally and, frankly, it continues to irritate me so I can imagine what it does to a competitive player like him.
Where do you go though after years of plying your trade at a club that has showcased your skills for so long? Like you, I thought of Dortmund, Juve, Milan or even the new kids on the block, Monaco. He's Italian by birth so maybe an Italian club but Serie A has lost it's allure, IMO. City makes some sense, especially with Txiki there
Pain, it would be physically painful to see him leave but I'd understand it. It's wrong how he's been treated even if Xavi came out to try & ease the tension. Mazinho has been a pain to deal with but I understand his frustrations. Still, he's not going to get into Del Bosque's WC squad, I seriously doubt it - regardless of where he goes. The midfield for La Roja is set (Again, unless there are injuries).
As for United, much rather you lot took Cesc. Plus, I think he'd serve you guys better than Thiago