Psionics should be optional rules, implemented as a feat which grants you psionics when you first take it, and gives you more powers as you take it multiple times, and supplemented by metapsionic feats, and be based around power-points. I think psionic abilities should be divided into minor abilities, which function like minor spells, lesser abilities, which require power points equal to their level, and greater abilities, which require power points equal to twice their level.
Example idea:
A fighter takes the aforementioned psionic feat and gains power points equal to his highest mental ability score, adding 2 every time he gains a level. He gains a number of psionic abilities equal to his highest mental ability score modifier, none of which can be of a higher level than him.
