I don’t think such a function will help much. If someone is aware of the secure ISR breaking anything he will adapt the priority. If he isn’t, he’ll probably also not call the extra port function which would tell him that.
I think making securePort_DePrioritieNSExceptions()` a configuration option is the more straight forward solution.
For debugging, maybe a directly callable assert to “check ISR pirority”, defined in both secure and unsecure world, could help, but that’s probably not a FreeRTOS feature.