As for systems, I have a feeling that Benitez will play 4-2-3-1 next season when he has his best 11.
An example of that would be:
Dudek
Finnan Carragher Hyppia Troare
Hamman Alonso
Gerrard Garcia Riise
Morientes
This is a system he used mostly in Spain and is also the system he has used when Gerrard, Alonso and Hamman were all fit. I don't think it was a case of fitting those 3 central midfielders into the team, it was actually the case of Benitez picking his first choice.
He likes one striker playing very deep off an advanced front man and Garcia is best in that position.
Even if Hamman goes in the summer I still think Benitez will buy in a decent central midfielder and replace him.
In certain matches Benitez has dropped Xabi Alonso and played an extra forward: at the start of the season this was Baros.
Its interesting and no one knows what players we'll have next season, but I'll wager the system Rafa is aiming for is 4-2-3-1.