I'm not into security as such so can't really comment. FABs are indeed good provided you've your own designs that you can mass produce. Besides being a new comer the new FAB would have to compete with the old guys in Singapore and TAIWAN. They have optimized their operations through decades of running. The main point being who will utilise Pakistani FABs when they can get the job done effectively in Singapore and China. In fact that is one of the reasons why our own(India's) 10-14nm FAB could never really take off. Kindly note, unlike Pakistan India does have designed various RISC micro processors and have been operating a 180nm FAB for sometime now, yet we couldn't setup a 10-14nm plant.
So in order to make Pakistani FAB even meaningful(let alone profitable), there should be enough R&D activities pertaining to design of ICs first. Once Pakistan has breached that threshold then they can go for a mid tier FAB something on the lines of 180nm process. But even that is realistically decades away. Don't take me wrong, itz just the financial reality.