I like all of these ideas. I think the proposed ideas can be grouped in one of three categories:
mind-to-mind:
"Panic" (-->vanilla)
"Mind Control" (-->vanilla)
"Mind Blast" (deals Damage, and/or perhaps Stun Damage)
"Blind" (decreases vision? reduces accuracy?)
"Fortify" (increases morale)
"Psionic Intuition" (reveals enemy locations)
mind-to-matter
"PSI Ball"
"PSI Blast"
"Force Grip"
"Telekinetic"
"Telekinesis"
"Psionic Shield"
supernatural / spirit-stuff / don't know-what-to-call-it
"Translocation"
"Astral Projection"
"Psionic Healing"
"Pyrokinesis"
I think the "nature" of psionics as used in vanilla X-Com is mind-to-mind-effects. I don't really feel that any of the others fit with the general context. I still like them, though, and I think that (for other conversions and mods) the mechanics for these should be implemented.
Maybe the hardcoded "weapons" of the terror units could also be included in a system like this? most of them are more like "abilities" anyway, aren't they? they cannot be unequipped; they have unlimited ammo; they are only available to certain units (the reaper's bite attack, for example).
perhaps it would make sense to implement a true "ability" system that can be used for this? the units could simply have an "abilities" field, and somewhere in the ruleset those are defined, with cost, effect, damage (where applicable), range (where applicable) and the like.
(with this, some aliens could finally become what they were supposed to be: take the celatid, for example. it is supposed to move towards hidden humans by detecting their brain waves. also, it is said to be able to clone itself: perhaps it would be possible for them to have an ability "mitosis", which allows the creation of a second celatid - replacing the original celatid with two that each have half the previous health, combined with a slow "regeneration" ability...)once we have a system like that, possibilities could become endless...