peek/poke or other method to write direct into nrf52 registers?

Neat! I hope you're handy with a soldering iron then :)

It's frustrating about the pin swapping - it's something I wanted to do originally (hence the capacitive sense in the KickStarter) but the reboot just didn't seem worth the hassle.

Also, that example uses nrf_nvmc_write_word which implies that it's flash memory? If so you'll need require("Flash")