My dear friend (I don't know your name as of yet), while I agree entirely on your assessment of Marchisio, I don't see us playing a 4-4-1-1, as we would be wasting 3 of our 4 strikers. We should play to our strengths, and in that respect, the 4-3-1-2 is the best possible formation, even though it still poses some questions and presents some potential headaches.
Important things you must note:
1) We will not bench Melo; we paid a lot of money for him, he will start, and he deserves to start. He can defend, tackle, as well as distribute the ball, so he is a very welcome addition to our midfield.
2) We cannot afford to play with only one striker, as that would imply limited playing time for 3 of our 4 strikers. Furthermore, Del Piero cannot properly function in a 4-4-1-1 (unless you plan to play him behind the lone striker, but then what will you do with Diego?!), and he can't play on the flanks in a 4-2-3-1, so we need to play with 2 strikers.
3) Del Piero will be a starter, so the one striker solution is not a viable or feesible option.
4) In your 4-4-1-1 you propose playing Gio on the left, and Camo on the right. The problem with that is, Gio prefers to play a little further up front, as a left sided attacker in a 4-2-3-1 formation, or as the ace in the hole (no cheesy comments please

) in a 4-3-1-2 (alternating with Diego or even Del Piero for the role of support stiker or 2nd forward). Camo, on the other hand, has been quite unreliable, inconsistent, and injury prone, so I am not expecting much from him this season. However, he can give us that impetus, that push off the bench.