Multiplexing different circuits to one output pin - isolation methods?

[max_torque]

I have a device that has multiple "channels" where each channel can be software selected as to what that channel's function.

One function is a high side output, using a smart switch, this is a low impedance (50mOhm) output of system voltage, which is normally around 28v, but can be  as much as aropund 45 volts under certain cases

A second function is as a precision Thermistor, where there is a precision current source (at between 1 to 5 volts depending on thermistor used and the temperature of that thermistor)

This means that the thermistor circuitry needs to be isolated from the high side switch circuitry, and the up to 45 volts that could sit on the pin due to that function.  What i need is ideas for how to achieve this.  Currently top of the list is using SSR's (60v & 100mA rated) that "hide" the thermistor circuitry behind those solid state devices.  Are there any other options?  Such as high voltage analogue multiplexers or similar?  Cost is not that important, but i'd like to avoid a complex jumble of descretes and physical relays are a no-no due to the devices environment (high vibration).  The SSR option also conviently means the switch on signal is not referenced to the voltages on the output pin and hence can be directly driven by the micro

typical SSR:

https://uk.farnell.com/vishay/vo1400aeftr/ssr-mosfet-60v-100ma-full-reel/dp/2369247


The on state resistance and leakage needs to be reasonably well controlled between -40 and ideally 125 degC (i'd except 105 degC) to avoid messing up the thermistor drive current.


Any other options / ideas to do this isolation / switching?