If your boards has a full breakout of all the pins, I could do a dirty hack.
Since BNO055 and BMF055 are basically the same, you can keep the MCU in reset state with the reset pin, and use the direct SPI connections to communicate with the 3 sensor ASICs at high speed to get raw data. These pins are marked as "reserved" in the BNO055 datasheet, but in the BMF055 you can see the internal schematic.
Seems like you have a nice logic analyzer. What is the maximum speed your are able to get, considering the clock stretching ? If you could grab a logic analyzer screenshot of that test I would add it to the Q&A section for others