If you realize how many variations of F-16's there are, then you start to understand why a company would limit itself to doing just 1 version. There are a lot of blocks of F-16's. A models, 1, 5, 10, 15, 20(FMS), and that's not including any sub blocks of each of those blocks. C models, 25, 30, 32, 40, 42, 50, 52, 60(FMS), and again not including any sub blocks or the many avionics software and hardware variations. It's taken ED this long just to do 1 block with a particular avionics software/hardware config. So adding in all the other possible variations, is a task that would be insurmountable by a company that also does more than a single high fidelity airframe.
FMS=foreign military sales, aircraft not owned/operated by the USAF