This sounds to me like the kind of feature that would have to be handled by the kernel. You can’t modify the kernel itself but you can provide call outs at boot time. Even so, if it can be done at all, this sounds like it would be a challenging feature to implement.
You could approach QNX about this but at the very least you will need a support contract. It they are willing at all, it is likely they would ask for a large cash payment. That seems to be the way QNX works these days, coin opperated.
But there is a reason to reconsider this entirely. I’m not sure if it is the same feature, but I have a gaming computer with an Intel processor, and it can boost one of the cores to a higher frequency at the expense of the other cores. What does that do to the scheduling algorithm in a real time OS? Would you have the OS always running the highest priority processes on the higher frequency core? That could cause process migration issues. If not, you might be letting a lower priority process use a higher value resource.