Pak doesn't need an assault aircraft carrier - what aircraft carriers are today. It needs a defensive carrier similar to the Soviet and Italian concept. It needs a carrier to use as a foreign power tool to get funds from Gulf and other rich states (Gunboat diplomacy).
So, the real question is, how can Pakistan get a low-cost, defensive aircraft carrier?
The first is to understand that modern carriers are built for fast, heavy jets. If you lower the requirements, you can build a cheap and small aircraft carrier.
You can convert a small tanker into an aircraft carrier. A carrier where fast supersonic jets will not land, but one where light, small aircraft can. Aircraft like an armed turboprop, a small turbo-prop transport, helicopters. These armed turboprops would be able to perform like the S-3s, low cost, cheap and endurance basic air defense, anti-ship, anti-submarine, and close air support.
Those functions alone would be a gigantic boost in capabilty and would allow Pakistan, for instance, to become an instant regional power that can bomb dysfunctional countries. For instance, Yemen, at the behest of Saudi.
What would such a low-end aircraft carrier cost?
Weighing at only 10,000 tons, and built from a small used oil tanker, such an aircraft could cost between 100 million to 200 million USD. They would be easy to maintain, as the main cost of an aircraft carrier is the fuel and upkeep of fast jets.
4 helicopters, 6 armed turbo props, two transport turbo props, 8 UAVs and you have a solid capability that can add to any medium sized fleet. At pennies to the dollar - couldn't ask for a cheaper rate.
Some additional advantages
1. Since anti ship missiles are subsonic, they would be able to pick them off long before such missiles would get close to our own fleet. So, they would be a serious long range air defense capability
2. The fleet would be able to base large and capable UAVs in a wide variety of roles, something even destroyers cannot do effectively.
3. They can do anti submarine warfare for a huge area and very effectively. Saving on ASW platforms.
And imagine the prestige of owning an aircraft carrier.