All of the Talents use psi dice in some way-- deal d8+[p] psychic damage, make a check and add [p], create up to [p] dancing lights, that sort of thing. No Disciplines do, though. The only interaction there is the Mute Display Talent, which basically gives you subtle spell if your psi die roll is equal or higher than the number of psi points you're spending.
It would be easy enough to add the psi die to some discipline powers. Changing xd6 to (x-1)d6+[p], or 1 minute to [p] minutes, won't really harm balance. I don't think I could apply it to every effect without serious pain, though.
Looking at ways to plug it in systemically... the only idea I have is to relate it to psi limit. The psi-points-spent-in-a-given-action would remain constant, but at the beginning of each turn, you roll your psi die, and that's how many additional psi points you can spend before the beginning of your next turn. (And the number you use when you're rolling for Talents). That would give a sort of ebb-and-flow to your psychic power.
...but eh. The more I look at this, the more I think I should drop psi dice as a mechanic altogether. Or at the very least update them to match the published Psi Warrior and Soulknife. Which I guess would be something like:
- Instead of
spellpsi points, you have an equal number of psi dice.- Talents mostly don't use psi dice at all; for stuff like Psychic Aptitude, it can just be "roll one of your psi dice," rather than expending them.
- To use a Discipline power, you have to expend a couple psi dice (ie, the same number as you'd normally spend
spellpsi points)- When dealing damage with Discipline power (or Talent?) you can expend additional psi dice, up to your normal limit, and add them to the damage. If nothing else, that would save a lot of repetitions of "you can increase this ability's damage by 1d6 per additional psi point spent on it"...