I don't see a problem. Having 4 replacements for the 4 attacking players is no different than having 4 replacements for the 4 defenders or 2 replacements for the two central midfielders. Last year we had 3 replacements for the 2 staring CBs (Barzagli, Rugani and Benatia for Bonucci and Chiellini), and if we buy Matuidi or any CM, we will have 4 replacements (Khedira, Matuidi, Sturaro, Bentacur) for the 2 starters (Pjanic and Marchisio).
Last year we had no alternative for a tired or out of form attacking player (which all of Higuain, Cuadrado and Dybala were in the last month of the season). Now we're solving this problem, and we're doing it incredibly well.
Adding a good CM to the squad is also important and it seems to be in our team's plans.
The defense might suffer the most. As average as Dani Alves was when he played RB, we didn't upgrade on him there. The main hole, though, was left by Bonucci.