Why would we dismantle our team? We know that Pjanic has dependency issues, he can't help the fact that he's from Bosnia, but even at his worst he's good enough for our midfield and at his best he is a force.
And if you check out who he has to run for him it can't be compared with what Pirlo had. Vidal and Pogba as opposed to Matuidi and Khedira. Several steps down on both positions, both in terms of stamina and intelligence.