what about the LOC110 from Clare with just a series resistor to the diode (diode current linear to Vin). Remember that you need a "high voltage resistor".

Then read the transistor current (internal or external a/d) and linearize it in the uC,

That would be my approach (I see this as being the closest to KISS).

put it in 2 enclosures, then the LOC110 will guarantee that the box with the uC never get electrocuted (at least if you do a reliable design)

I had a look at the LOC110 and found the isolation to be to 3750V. I expected much less.

Erik