I see only one problem that is CPEC pass through POK that is a part of India. India claims it similar like China claims Taiwan. This is also a huge security challenge for India as Pakistan has been attacker and imposed four wars on India along with terrorism since last 30 years.
If you see the map of Pakistan and proposed route of CPEC, you will easily notice that CPEC road passes through the region that is near Indo-Pak border and all major Pakistani military facilities lies behind this line. In the case of war, Indian forces will have to cross CPEC roads and that would give China a reason to help Pakistan in the name of protecting CPEC.
This can not be an economic corridor as two countries economy can benefit only when both the countries are economically stronger or equal. Prove me wrong.