I still wish I could find a FET like the one I originally specified, but the analog switch will work. I know my device will have to operate at 70C. But there is some chance of intermittently going into ~125C environments (it happens...). It's easier to predict how a FET might behave at high temperatures.
The problem is most vendors spec FETs for the mass market uses, so they only give a very conservative MAX and little else.
With analog switches, you have more chance of finding specs for leakage, because that matters for some users.
eg I see Nexperia XS5A1T4157 gives typical of 20pA at 25°C and max of 320nA at 125°C
A somewhat similar NMUX1237 specs typ 2nA (25°C) and MAX of 55nA at 85°C and 490nA at 125°C, so you can see the temperature effects.
Others you could test.
I see a cheaper GT4157S6 from GTIC at lcsc that specs < 1uA at 125°C