No, we can't play with just one defensive midfielder. With Rothen traveling down the left flank, and Zambro down the right, this will leave Tacchinardi/Emerson all by himself in central midfield. Thus, holes will be created if on of the more forward midfielders gives the ball away. Against good teams, this lack of coverage will cost us dearly. Not to mention that both Oddo and Evra are almost as likely to go forward as Salgado and Roberto Carlos for Real Madrid respectively. So with all these players going forward, even a ten man Monaco side could find a way to score if someone gives the ball away in midfield. One bad touch could possibly leave Emerson/Tacchi, Ferrari, and Mexes in a tough situation. Don't get me wrong, I love attacking football, but this IMO is over doing it. We would get smashed on the counter-attack many a times.
I think a better, more balanced side would look like this:
----------------------Vieri---------------------
-Del Piero----Nedved(Rosicky)---Fiore-
-----------Emerson---Tacchinardi--------
Zambrotta---Ferrari--Mexes---Oddo(?)
In this formation, there is a great balance between attack and defense, something that all good teams must have to succeed (well, except for Real). My (and your) thirst for attacking football would be quenched, with that triumverate of attacking players, who could move freely behind Vieri or Gilardino. But the side is well covered for the counter-attack, with Emerson and Tacchinardi in central positions. If you have ever seen Roma play, Emerson almost plays in a subdued free role in central midfield; I see him traveling into more forward positions regulary, and Dacourt is kind of like Tacchi in this set up, who both do the holding roles. Emerson's main priority is to make sure there are no holes in midfield, but if the time is right, he could travel up into the box and create chances. This is what makes Emerson such a special player. As I have said before, Emerson is a creative midfield destroyer. I think he could be just as good or even better than Davids in that role.
Not that I don't like your set up, I just think it is too risky, especially for the Champions League where balance is the key. And with Prandelli probably taking over next season, we know he likes the 4-2-3-1, with two holding midfielders.
I know some people might not like this more conservative lineup, but it is one that can produce offense, while keeping sure at the back.