This reminds me of another way to deal with this, though it could be a lot of trouble to set up. QNX 6.5 supports the partition scheduler. That would let you run a 2nd partition which would be guaranteed some amount of cpu. If nothing is running in that partition the cpu cycles aren’t wasted.
Unfortunately, I don’t think you can just start the partition schedule in a running system. I think you have to build it into the boot file so the OS starts with running.