I'm intrigued by this. Bringing Wilshere in would change the system & style of play as he would look to get forward & create more than Barry. Even if Wilshere was told to sit deep and spray passes he wouldn't be the break it up, pass it on man that Barry is.
A midfield pairing of Rodwell & Wilshere could end up similar to the Lampard-Gerrard axis...both are happy to try to do their defensive work but they're going to have to subdue a natural tendency to drift forward and create (Wilshere) or make attacking raids (Rodwell). If an understanding is struck and only one of these happens at once it could be sensational...but if not it will see us open to simple counters through the middle of the park.
I agree with your comments re Walcott, he's really upped his game since he's felt the Ox breathing down his neck. With Chamberlain (and maybe Sturridge) to come on late in games we have the potential for devastatingly quick counter attacks - if that pace & trickery is harnessed correctly.
As for Cahill as captain...well I laughed when I read it, though that may have been a slight overreaction. Not this summer for me, I wouldn't particularly even want to start him this summer. Given a couple of years though and - most importantly - regular games at Chelsea and he could be the man to lead us in Brazil.