If Grosso really come, then we will have 3 LB. So who do you think that we will sell, DC or Moli? Personally, i think DC have the same playing style with Grosso. Those two have ability to support attack (crossing, pace) but lack of defending skill especially defending positioning and ability to return when opponent do counter attack.
and Molinaro is the opposite. He can't cross and pass. but he have pace, and physical attributes. and u can see that he can be good when he doesn't need to support attack (remember Madrid and Inter games)
It will be confusing. Actually i prefer to have Moli so we have 2 kinds of Full Back and that we can play them based on Ferrara needs. but DC has more potential to develop as better player and has more talent.