Interesting discussion, I was away for a while. Was busy getting Married....
The Internal Combustion engine is here to stay. So, any car made in Pak, should be IC engine running on Fossil fuels. Its been more than 120+ years since Petrol Run engine was invented, it has outlived, the Electric Engine, which was invented around same time. So, the method of fuel may have enhanced with cleaner burning fuels, but the basic engine is same design as the first Internal Combustion engine. So, no matter what will be the source of its energy, Gasonline, cleaner Diesel, or CNG, or even Hydrogen, or whatever, it will stay.
Now the Motown Brother's idea of car built around CNG has solid ground. The vehicle should also have an auxialiary fuel tank for Petrol, as most people do keep Petrol in the Tank of the cars as well, specially for the drive on hilly areas. I have visited Murree Last week, and all the cabs and car I noticed, even on mountainous Hilly region like Murree were on CNG or Diesel.
The Diesel is also second best option, considering cleaner burning Diesel, specially for hilly areas, as I was in a car with 2.0 Diesel engine climbing hills of Murre at 7,000+ feet altitude in 3rd gear with ease.
So, to keep the discussion on track, the CNG is currently most popular source of fuel in Pakistan, and also gaining popularity around the world. As far as natural gas reserves are concerned, there are plenty of reserves to feed the need for many centuries. Pakistan is already in talks with Iran to use its gas, as most of you must be aware of the Iran, Pakistan, India, Gas Pipeline in works, and another Gaspipeline which is under consideration is Turkmanistan, Afghanistan, Pakistan line. So, there is no lack of Natural Gas it will still be economical while importing it.
The design of the CNG cylinder should be such that it be a multirole design. Forexample, the Cylinders could be built inside the Chasis steel bars, while being safely built into the car body, to support its frame, the hollow steel frame can also store the fuel. In case of crash, it should be made in a way that it does not explode and engulf the whole vehicle floor. The cylinder stowed away in trunk has that element of safety, as it will be away from Sparks and crash forcees.