A good rule of thumb I think is ask yourself: Does this edge or change ever allow a psiad to meet a psion head on in their area of expertise. If so, it's probably not a good idea*. A psion facing say, a biokenetic should never be able to fight them on an even basis as a biokinetic, but do something clever with say, merging their biokinesis with another field that has their enemy going "how are they doing that?"

*With the exception of alternate settings. A world in which psiads have evolved past their limitations, could be used, but in that case psions would be the limited...