Schema for protection system
This is a very simple thing to do with a small microcontroller.  The on and off buttons would be just inputs to the micro.  The micro would sense AC power via a opto-coupler and control a relay that switches the AC on/off to the equipment.  Even a small PIC with internal oscillator can do this easily.

Of course if your client can't even afford a "smart relay", then he can't afford to pay you to create something different.  This kind of client is way more trouble than the little profit you might make.  He'll always be trying to push you on price, and second guess everything you're doing thinking you're trying to take him for a ride.  Run away.