I think you can just set the I2C pins in MyBoardNRF5.h without remapping the pins in MyBoardNRF5.cpp.
Look in MyBoardNRF5.h, under the Wire Interfaces section. Set SDL and SCA to 30 and 31 as appropriate for your board.
Hope will test the new version of this universal board soon. Now it has additional inexpensive accelerometer, magnetic sensor, led, reset button, multifootprint for lora/hw/cw radio without adapter and improoved 4layers design