I do get this, and I can certainly appreciate. But, just to bring up the counter argument, if they don't use spells, but instead go with some completely different mechanic, then I think it's going to be a much steeper uphill climb to convince the majority that we need psionics. There are some who look existing spells, and they do have a point, and say, "Well, with magic, you can mind control, lift things from far away, communicate telepathically, etc, why do we need a shopping list of completley new spells (err powers or whatever they call it) that do essentially the same thing?"
It's not an unreasonable point. What effect is uniquely psionic? (Heh, this runs the risk of diving back into the genre discussions from the other thread. Please, let's not go there)
This is a fair argument. I think the separation of psionic abilities from spells for a whole class is a pretty significant design endeavor when the whole process is going to be hemmed in by having to stay 6' away from the current spell rules at all times. One way to accomplish that would be to pare down the actual number of psionic abilites, perhaps into a set of ability families, but provide significantly more gradients and nuance then you find in similar spells within that family. Telepathy/Mind control, for example, could be a rich source of related abilities that really get granular about what could be done with the power. You could tie in a lot of specific conditions and outcomes that escape the spell equivalents, and you could also make a system where effects can be combined.
If, for example, a Psion had the ability to do psychic damage, something like command or suggestion, plus apply conditions like stunned, fear, paralyzed and the like, and the ability to scale powers to effect multiple targets (from a variety of chosen abilities), you have some very fine control and choice as a player about what the outcome of your ability use looks like. Obviously you don't want to fall too far down the rabbit hole of custom effects, but I do think there's room to make it feel different than spells. At the very least, you'd have the
Wizard's can do this, but Psions excel at it angle.
To take another example, lets look at the idea of illusion. Wizards create illusions visible to all and that's basis on which those spells have effects. A Psion might also be able to create illusions, but only in the mind of the target. Handled right that could feel very different, and it would also have a different set of possible applications. You could probably allow a lot more detail, with all the sense involved, and scale the ability by number of targets potentially affected.
A third example would be telekinesis. The Wizard does have a suite of spells that have telekinetic effects, but they aren't offensive generally, and the use of each spell is pretty tightly constrained by the spell description. A suite of psion telekinesis abilities could have a lot more offensive capability, as we've seen in some of the subclasses in the UA, and also have more general applications because it could be a lot more flexible in application. The ability to use them to interact with encounter environments in a more flexible way could be a great tool, and it would feel different than the spell equivalents. The example here is probably Jedis - if you can lift, topple, throw and otherwise interact with the entire diagetic frame, the ability has a very different flavor.
Anyway, those are completely spitballed ideas, but I think they index some of the potential pretty well.