In the OT we see officers which are definitely not clones, so why do we assume that all stormies are clones? If they are all clones then I doubt that they are still all clones of the same man, more then likely they are clones of multiple, probably thousands of different soldiers, but with the same programming ingrained into them. Let's face it, the sheer number of troops needed to subjegate a galaxy would make a strictly cloned army a logistical nightmare. Instead you start with your clones, recruit from the locals to build support and slowly pull the clones back to more essential positions. The clones were perfect for establishing the empire, as they were preprogrammed to be loyal to the emperor and were spread out all over by the clone wars. But in order to maintain an army the size that we are to assume exists you need to recruit from the locals, or at the very least build hundreds, if not thousands of more cloning facilities, which raises logisitical concerns of its own.