I think Dortmund have shown us tonight what picking out a decent system and then signing players what suit that system can achieve. Its the same with Juventus playing their 3-5-2 the reason it works is because they have the players that suit that system. Tonight has just shown us that we need to find a formation that can suit our most influential players and build around it. I understand the need for a plan B but IMO that should be simple and going 4-3-3 or 4-5-1 depending on the circumstances. I doubt anyone would disagree that 4-2-3-1 is our strongest formation but We get away using this formation in the premiership as a lot of teams play defensively against us but in Europe we will be found out. The main problem we have is that the system is impossible to fit all of our best players in it whilst getting the best out of them. To successfully use the 4-2-3-1 I think you need a solid back 4, two composed holding midfield players, two fast tricky direct wingers, one playmaker and a poacher up front. Now we do have certain players who will relish playing this formation however I think we will not get the best out of players like Yaya, Nasri, Tevez and even to some extent Aguero.
Yaya is IMO the best midfielder in the premiership by a mile however I think he struggles in a midfield 2 and by playing him in the advanced role it means we have to play Silva out of his best position.
Nasri I think he plays to narrow to be on the wing in the formation and does not have the work rate to allow Clichy to constantly bomb forward. I think in the formation he would suit Silva's role but is he not as good as Silva.
There are better options than Tevez and Aguero to lead the line for us as Dzeko and Balotelli are more suited to playing as the lone striker. I do think Tevez and Aguero would play well in a 4-4-2 but that leaves us in a catch 22 situation as players like Silva and Yaya don't suit a 4-4-2.
Overall I think we signed players based on their ability at previous clubs without looking at their adaptability to our formation. Dzeko is the perfect example of this as if he were at Spurs or United he would be a 30 goal a season striker. And untill Mancini decides to drop a few big names unless they adapt to our formation then we will not go far in Europe.