I have a circuit as seen in the schematic above. It has 4 different output stages. Each one has an "Enable" pin. The user is able to freely use the mechanical switch to enable any of the output stages. When an output stage is not enabled, its all output pins become Hi-Z. All output stages have a common output connector, and their output pins are shorted together at the output connector side. Therefore, only one of output stages must be enabled at the same time. According to the datasheets of the ICs I used in the output stage circuits, the output pins tolerated short time period of short circuit. So, there is no need to handle the transition between different user choices.
Now, my problem is, I don't trust the mechanical switch. If it fails and enables more than one of the outputs at the same time and it stays like that for a long time, there will be big damage on the circuit.
Can you suggest me a logic circuit which uses least amount of ICs to guarantee that always only one of the enable signals will be logic-1?