Design assumptions:
-RPI PICO with LCD ad controller
-usage of precise ADC (MCP3910) to measure voltage on DUT and precise resistor
-max +/-200mV on DUT
-kelvin clip connection
-DAC (MCP4822) controlled bidirectional current source (+/-3A)
-3x 18650 lipo for power supply
-as high resolution as possible from above configuration
Above analog part was simulated.... time to draw PCB and order the parts
Optional possibles/TODOs
-bulid-in BMS (charger and balancing)
-nice case
-find and order suitable parts
If you do the error budgeting you will find out that precision op-amps are not quite necessary for this project. Any modern-ish general purpose low voltage op-amp will work great. Even the lowly LM358 from late 1970s will work well as long as the ambient temperature doesn't vary too much.
Inspired by your project, I’ve made a first version of my own take on it: https://hackaday.io/project/191204-sdo-milliohm-meter-v1