I had an idea of using 3 IMUs placed at 90 degrees to each other, using the accelerometers and combined gyro data to check the gyros against drift. The accelerometers would confirm no movement, and the output of the individual gyros would somewhat self-correct because they all won’t drift the same direction, at the same time, because of the orientation. So if X1 (X on gyro 1) started to drift, which corresponds to Y2 and Z3 (example), and they respond with not the same data, the sensor or input can be reset/adjusted.
Not sure if it’d even remotely work, just an idear I had and haven’t gotten around to building/testing yet. Does your experience indicate if this even remotely viable?