A very interesting post, TG.
I agree. I think that we can safely say that both situations are principally agent driven. I do think that there might be a kernel of truth somewhere re cesc's 'homesickness'. But he was ambivalent about his 'dream' when he came to Arsenal, and has undoubtedly benefitted from that decision. I think the 'emotional' issue is far more likely to be an understandable desire to be in the team touted as the best ever - that would exist whether that team was Real Madrid; Bayern Munich or Porto.
But my theory is that the PR/agency aspect for Fabregas is dressing this desire up as a desire to return to his hometown - because that sounds less disloyal. Can we blame the player? Well I don't share your antipathy. The saga has been protracted, yes. But is this down to Fabregas - or is it down to a Barcelona management who have made it thus by simply failing to make an offer we can't refuse? I'd say the latter. And I'd say that the saving grace for Fabregas is that at least he has given us many years of loyal service. That is not a total excuse - after all he owes much to the club. But set against the modern standard set by the likes of Rooney; Tevez; Robinho - for me Cesc is not the worst of offenders.
IMO Nasri is a different matter. I agree with your analysis of what is driving his behaviour - and on the one hand its understandable that he sees this as his shot at the big time. As Adebayor; Flamini and Hleb did before him. But what I don't like about Nasri is that it is more calculated and opportunist even than his predecessors. He refused to negotiate a contract extension last Summer - when he had not exactly set the world alight - and is looking to hold the club to ransom this Summer - on the back of just 4 months' performances that justify the kind of money he wants. At least Adebayor gave us a more or less a season. Nasri's move suggests strongly that he only ever came to us as a stepping stone, or to raise his profile - and to exploit the very first occasion on which he showed some form. So for me he is at the cutting edge of the modern football mercenary movement - yet unlike his fellow ground breaker, Rooney, he doesn't even have the 'decency' to give the club anything before baring his teeth. He is the difference between a woman that you meet in a bar, buy champagne all night and then take home for great sex, and a 3 minute lap dance.
Which is why, if he stays, fans might feel 'relieved' that we have held on to him - but he will never IMO be regarded with any fondness by the fans. And I don't think he gives a damn, either.