It's easy to calculate the change in center of mass due to fuel consumption.
But suppose you want to probe it experimentally (with whatever necessary calculations you might need to do on the measured data).
Could you do this with accelerometers/gyros alone, e.g., if you had an array of them? Could you do this with some other type of (off-the-shelf, easily accessible) sensor? Say maybe you want to try this on an ROV with variable mass and you don't have a good estimate for the rate of mass change handy.