I've have a setup where I have I2C bus range extender to control IO Pi Plus from the distance of 30m. The I2C range extender has it own power and it provides +5V, ground, SCL and SDA pins, nothing else. I noticed that this poses a problem as the +3.3V is missing and I2C level converter seems to depends on it. I solved this by building voltage divider to feed also +3.3V from the +5V.
My question is: Have you thought that future versions of IO Pi Plus could have voltage divider built in, so users could only power the board via +5V, ground, SCL and SDA pins? Or am I missing something here?
If you or anyone is interested, I'm using this range extender: https://shop.controleverything.com/products/long-distance-i2c-bus-extender
Seems like these are bit hard to find from Europe. Maybe AB Electronics could build one of their own in the future :)