Bro that is not how the legal system of the world works. You would not be getting any inflated billions from abroad. Better to write them down off. And just for the sake of argument, even if we do get them, I doubt they will change the course of our nation. We have now developed a very unhealthy habit of blaming everyone else except us for our problems.
Now, you need to create economies of scale as pointed out by many poster to distribute the cost of manufacturing such an airplane. A logical plan would have been to build small scale passenger gets and market them in PIA and other domestic and international airlines. Then we can use a cargo version of that same air frame and full fill our needs. However, not all such initiatives for indigenous manufacturing goes according to plane. For reference, read up on the Indonesian experience in launching a homegrown car and aviation industry.