Hack an Andover TAC Temperature Sensor?

The HVAC people came by a year ago (or more), and installed a temperature control for the Air Conditioning unit in my office. It's *horrible*. We can't turn it off. It only allows us to vary the office temperature between 75 degrees and 83 degrees using a slider on the front of the sensor. It's now always too damn hot in the office, and I can't work. HVAC people say they can't take it out, and that everybody has to have one in their office.
I want to hack mine. I took it off its mounting (tiny Allen screws), found the model number, and photographed what I could. Now I want to know how I can either

1) install a different sensor with an on/off button (which I'll have to buy myself, but who cares)
or
2) hack this so I can turn the sensor off and on when I want.

Any suggestions?