I am going to try both opto-isolators, and the TPIC6595 discussed below.
For the opto-isolators I planned to use an arduino to sense a switch, and if closed, turn on a 24V lamp on the existing panel. Here is what I was thinking.
The LED D1 was just to let me see if the Arduino was sending out a signal that should illuminate the lamp.
Am I headed in the right direction?