Investment will only happen if there is a long term commitment on the part of MoD to encourage local production. The route is simple, license production from kits, deletion through local parts, and then upgrade and evolution to a better variant that can be labeled as ones own indigenous production. But to do this one needs long term contracts and commitment towards indiginization.
The easiest to do is local production of Trucks and MRAPS. Identify a heavy duty chassis, pick out a powerful engine off the shelf, look for a robust axle, and carefully select a differential/gearbox to go with the engine train and the axles. Mate them on the selected chassis and the rest is all design and metal fabrication and mechanical integration. The armored sheets can be imported first then we can ask Special Steel based out of Karachi to work out production. Run flat tires can be imported. I believe bullet proof glass can be sourced within Pakistan or can be imported from out side for the time being.
If there is a robust demand for these MRAPS say over a ten year period, then PA should place an order of procuring X number of vehicles over a ten year period. The down stream industry that is producing autoparts like Balochistan Wheels (Allow and metal wheel rims), Agriautos (Shock absorbers and other parts), Balochistan Glass (Wind shields), Thal Engineering (electrical harness), The General Tyre and Rubber, Thermal Systems (Air Conditioning and heating) and many more, can then be included in the production and supply to this project.
I have made it seem a simple project but it can be done if the will is there. For starters we can look at GAZ trucks out of Russia that are robust and can be licensed produced as far as the chassis and power train is concerned.