First of all I don't agree with you at all that Mertesacker couldn't handle that role. In possession he would be the equivalent of when we play all those balls back to Mannone/Sneezey who then in turn just hoof it aimlessly forward. (Sneezey may pull off a rabona every now and then, but you get the point.) Per can do that role IMO and better recycle possession. Not asking him to be all creative and shit.
Defensively in transition: Mertesacker would cover for Kos or TV who in turn would have to cover for 'their' wing back quite often. Mertesacker's reading of the game is superb, and I have no doubts whatsoever that he could play this role well.
Defensively in a settled defensive shape: Mertesacker would always be the one who attacks the aerial ball. He would also function as back up when TV or Kos inevitably get it wrong when timing those early interceptions that they love.
Further up the pitch I think both Gibbs and Sagna are well suited for the wing back role. Good engines, good pace, mostly decent crossers when given a bit of time. We already rely on our FBs for width, especially down the left flank. In this formation we would have Kos or TV to cover down the flanks without leaving us too exposed in the center of the pitch. Good thing IMO.
From a striker POV I think our current options are better suited to play with a partner. Both Podolski and Walcott are good finishers, but not well suited to lead the line by themselves. I also think Ior would benefit from not being the only player in the box that defenders have to worry about.
We'd still play out from the back. We'd still need CMs that are good on the ball like Wilshere, Arteta, Cazorla and Diaby. There would also be room for CMs that are good at closing players down like Coquelin, Ramsey and Frimpong. We'd play with more width in attack though, and we wouldn't have to have our best finishers on the wing all the time. We would also probably be less exposed down the left wing because there is no cover for Gibbs/Santos.
