Just thinking a little about this,
If he's dead certain on going, and would be happier in ideally Spain (language). Then why not offer Althetico Madrid a straight swap for Aguero? If he's true to his word of wanting out for his family then he'll take the wage cut (not as if he'll be on pennies if he did) and then Ageuro can come and be on a normal (if you can call it that) footballing salary,
I know people might not be happy with that as Tevez is probably worth more than Aguero, however would it not be best to take a loss on his transfer fee and be happy that he's off our books and off our hands. We'd also save thousands a week on Tevez's wage bill.
His reasons seem genuine, so I don't wish to slag him off here. Just a thought.