There is no limitation. It works connected via Mavlink serial right now. There are just some issues that cause the smart shots to sometimes tilt in the wrong direction. See other threads here on Ardupliot.org discussing the ways to fix these issues.
Unless you are talking about running STorM32 on the flight controller and the problem would be space and horsepower.
To be more precise, running it natively on the autopilot. Is there enough resources left on cube to do so? Is there any interest even?
Again, to have the ability to simply plug in a couple of NT imus’ And NT motor modules to an unused uart/serial on a cube would be amazing. Of course powere would need to be derived from power distribution, but we are already using hardware in that fashion.
Keeping setups light, modular and as simple as possible is of value. This has been my focus with the Solo’s artoo gear and Ardupilot and storm32nt. Why, because they all already talk the same language, MAVLINK.
Arducopter is at 913k out of the 1mb limit imposed by the STM processor defect. So it would be too tight.