I can't help but praising the way transfers went, absolutely smart. I would be a tenth happy if Berlus spent 100M to buy Ibra + Robinho.
The way Milan keep transfer policy also means the general system will be respected.
We don't buy new player to change the system but to make it work better and more flexible. Yes, more flexible.
So I think
the core of Milan is still lying on the solid CBs pair & GK for defense, the creativity of Pirlo & Dinho with the protection of DMs.
From 2002, Milan have been well know for the ability of fielding more than 1 playmaker in the team and at the same time, having the world best CBs & GK to protect the result and the world class DMs to protect the playmakers.
In short, the main forces, the core: GK, CBs, DMs & playmakers.
We won trophies thanks to them, even when the fullbacks & forwards were normal.
In 2003, the fullbacks: Helveg & Kaladze were only good at defend.
In 2004, the fullbacks: Cafu was not the Roma's Cafu, Serghinho injured a lot, Helveg out & Kala switched to CB.
In 2007, the forwards: Ronaldo couldn't play in CL when only joined last part of Serie A, Gila was a disapointment, Pippo had only some flashes, and I find it hard to remember Oliveira's name. The fullbacks: Oddo was solid but he didn't help the attack much, Janku's defense was erratic and Maldini or Kalazde playing LB was of course not the right decision.
Fullbacks & Forwards are important but we won without them being good consistent, while the core was magnificent.
Last season, there were moments when we thought we could take the world without injury, but the injuries did happen. The core was weakened with Nesta's injury & the tireness of Ambro (when Rino & Flamini's performants were not good enough).
IMO, this season is building around: Abbiati/Amelia, Nesta & Silva, Pirlo & Dinho, Ambro & Flamini. Not around the fancy names of Pato, Binho, Ibra or Boateng, they are not the core, though they are important.
The core + world class forwards is the receipt of winning for Milan this season.
For the core: Sokratis & Yepes are CBs subtitude, Seedorf for Pirlo, Boateng & Rino for DMs, Ibra or Binho for Dinho.
If Dinho gets injured, the upper playmaker could be Ibra or Binho, but we'll play them at second striker in 4-3-1-2 and insert Seedorf at ACM.
The use of Seedorf is tricky, he could be in the core or not.
So Milan will have the line-up:
-------------------------Abbi/Ame--------------------------
--RB----------Nesta----------------Silva-------------LB--
---------------------------Pirlo------------------------------
-----------Flamini/Seedorf------------Ambro-------------
--Pato/Binho-------------------------------------Dinho--
--------------------------Ibra/Pato-------------------------
(Seedorf plays against small teams or sub in for tactical change)
If there is no injury.
The injuries of GK, CBs & DMs won't affect the formation, but:
If Pirlo gets injuried: The mids trio will be 3 CMs flat or with 2 DMs 1 CM/ACM. Seedorf is in the central, Merkel or Strasser may have their chances.
If Dinho gets injuried: We won't be forced to play 4-3-3

Binho is not so creative, Ibra is good enough but second striker is a bit far, so an ACM is needed:
-------------------------Abbi/Ame--------------------------
--RB----------Nesta----------------Silva-------------LB--
---------------------------Pirlo------------------------------
-----------Flamini----------------------Ambro-------------
--------------------------Seedorf---------------------------
------------------------------------Ibra/Binho--------------
--------------------Pato/Ibra-------------------------------
The core only is very competitive, the core + forwards is dominating, the core + forwards + fullbacks is a team of the decace or even century
Just my oppinion.