First off the whole reason is to cash in on Granderson and avoid the 189 cap.
Now, as to your claims of "They will have to get Hamilton" and "Not a Yankee outfield"
You know what... I'm not going to even start. You're just wrong. Hamilton will not be a Yankee and there is no such thing as a "Yankee outfield". I don't even know why I'm defending myself but I feel such an answer you gave warrants you to be smacked with logic and fact. Rendon is the best 3B prospect behind Olt on Texas and Castelleanos on Detroit, A Rod is made of glass and our next DH. OR, Rendon could even be used as part of a deal to acquire another big time bat who is young and under team control. Hmmm Stanton?
We are not keeping Granderson - deal with it. In today's market with the upcoming cloud of the $189m tax, getting a return as such is the most logical path to take. Honestly, we would not have missed Granderson all that much had that deal been made. He hits home runs and strikes out. He's the black Adam Dunn with athleticism and speed (which makes him way more valuable).
An outfield of Ichiro, Gardner, and Morse is one I'd go to war with any day given the current restrictions.
And I'm SURE.... SURE. That there will be a suitable 4/5th outfielder(s) the likes of Scott Hairiston and/or Reed Johnson on the team if for what ever reason Granderson gets cashed in on.
So with that outfield we'd be looking at MAYBE 32/130...from our entire starting outfield. With that production, ARod better hit 70/160.