Earlier quoted context omitted.
> It would be really nice to have a super simple processor with a standard architecture and tooling. Pragmatically speaking, that architecture already exists -- it's the 8051. (This part is a PIC clone, but 8051 is also extremely common.) RISC-V has promise for larger microcontrollers, but really tiny ones like these (48 bytes RAM, 1KB ROM) are better off with an 8-bit architecture.
Ya...8051s are literally everywhere, and there's a vast ecosystem of code and programmer talent to draw on.
Most of your code / effort will be in getting these peripherals to work. A ton of microcontroller programming is a simple if(voltage>0.5V) then {setup peripherals to do Y}.
In fact, voltage > 0.5V is a peripheral (aka: the Analog Comparator + DAC loopback) on most uCs today. So in practice its:
"If (analog comparator) then {do Y}".
Except "if analog comparator" is itself an interrupt that you put into the interrupt table, so that the processor can sleep for minimum power usage. So really its all just configuration of interrupt table handlers, configuration of various peripherals, and then a massive amounts of sleep.