The hardware is already compatible BMI263 supports external expansion of BMM150. You could see detailed HW connection in data sheet.
We're not actually using BMI263 and the replacement doesn't have that option. I wish we were, but I didn't get to choose. I was just using it as an example of an I3C IMU. My appologies.
Even if we were, our board layout doesn't allow us the extra lines to run I3C out to the IMU on the daughterboard and I2C back to the BMM150 on the main board.