While that sounds like it might work, you need to consider the design of these kinds of switch matricies. Often there are diodes that present a predictable voltage drop to the microprocessor so it can sense which switch you are trying to press. Simply shorting it may fool the microprocessor into thinking an entire row or column has been shorted.
If I were an Alaska Bush Man I would try this, for sure.
But I think you are better off simply replacing the keypad assembly.
You might be amazed at what kinds of parts like this you can find at the usual sources.
That being said, try this: begin with a Google search and see if I could find a service manual for the unit in question before beginning surgery.