The most fundamental miss here is the lack of live code editing. One of the basic things that makes PLCs a separate thing is that you can edit code live without stopping execution of the device. In real automation applications you can't shut down a plant or a line or a generator or whatever just because you want to add a new E-stop or change the timing on an actuator slightly or tune a PID etc.

If you have to kill the machine to recompile this is not a PLC by any stretch of the imagination, it's an Arduino with a fancy box.