Re: Shin-soo Choo?
Choo almost assuredly is not as bad a fielder as last year indicated, as he's not that old, and other seasons he has been more than adequate. He'd clearly be below average in CF, but his bat would of course more than make up the difference.
I'd much prefer to work this deal around Heisey and maybe another lesser piece in replace of Stubbs. Stubbs would fit the roster much better, as he could pose to be a perfect platoon partner for Choo (as he can't hit lefties whereas Stubbs is very good), and replace Choo in late inning defensive situations. Heisey really doesn't offer either of those qualities very well and therefore would be a much more poor fit as a back-up OF'der.
Choo would represent an upgrade, but I fear that there are much cheaper ways of doing so (ie. get a DeAza or Morgan to be a true platoon partner for Stubbs), and likely wouldn't have to give up the prospect of Didi's caliber).