We may need a low power industrial 8-bit MCU with Configurable Logic Circuits (CLCs) like some of the PICs have. When the NFC power is present we can wake the MCU up by connecting an interrupt pin to the Field Detect pin on the NTAG 5 and perform configuration. Then at all other times the MCU is in a permanent sleep state and the CLCs just do simple gate operations to drive the LED segments.
I was kind of hoping we could find an RTC with a simple built in driver to run the LEDs (like a purpose built one for a watch or something). That way we wouldn’t need an MCU at all and the RTC could just be set by I2C commands over the NTAG 5s transparent master channel. That might require some hit or miss sourcing from Alibaba though. China holds all the purpose built chips for their internal industry activity.