That pretty well describes the board in front of me ATM. Most of the system runs on a 20ms (I think) tick to manage the sensor read/evaluate/control loops, but there's a 10kHz timer interrupt always going that handles commutation of a stepper motor if it needs to run. 99.9% of the time, the interrupt fires, sees there's nothing to do and just returns.

for battery electric use cases it saves energy: you do just the necessary computations and you sleep the CPU until the next cycle. if little has changed you can sleep a lot. if a lot of rumpus is happening, you use the full cycle.