control multiple lighting contactors from multiple sources without turning everything on
Your third point binds you to one solution

Because they want phone or internet control of this system (and that is a reasonable request these days), you are absolutely married to a home-automation scheme like Wemo or HomeKit.  

That means you have two choices: you can build the other controls so they are locked in mortal combat with the automation... Or you can integrate the other controls into the automation using recommended methods.  Given that it's for a customer, you're pretty much forced into the second choice. If you are not willing to "skill up" in this area, get a subcontractor.