We have been postponing the acquisition of a decent RB for the past 10 years.
It was about time to make an investment there, it was a high priority to invest there and we rightfully did.
We bought a quality starter and unfortunately also signed a mediocre sub as well (by using the option to sign Motta) and we still have Grygera for depth.
I see no reason to sign a 3-4rd RB though, i would rather prefer a decent LB instead.
As for the midfield, we do move randomly there, i dont know why we are so panicked, we should first decide who to offload, do that and the sign the best we can according to our needs.
And you got it wrong, we wont play a 4-4-2 and we dont need more CMs, we already have Pirlo, Marchisio, Melo, Pazienza a few decent youngsters for depth and we are likely to sell Tiago and Sissoko. All these players are bound to cover just 2 positions in our squad, so they are more than enough.
From there, what we need the most is side forwards. Not like we lack solutions now (Krasic, Pepe, Quaq, Martinez, Iaq) but we are likely to upgrade our material.
I believe from this point on, our transfers will be upgrades to our current material.