JayPLC
You have a good start with your written description of how your process will work. Next you have to identify all the electrical devices which will provide you with inputs (example limit switches, level sensors, push buttons).Next identify all the motors, solenoid valves, indicator lights...
Good start. We are also contemplating wireless solutions. Security is our biggest issue although line of sight vs. transmission through and around tall buildings on campus is also problematical.
Check out http://www.iwasummit.com/ for information on a "wireless summit"