Skills: Knowledge (psionics) 8 ranks, Knowledge (the planes) 8 ranks.
Spells: Able to use least invocations.
Psionics: Able to manifest 2nd-level powers.
Special: Eldritch Blast +2d6.
Class Skills, Features, and Progressions: As Eldritch Theurge (Complete Mage), except replace all references to "casting arcane spells" with a corresponding reference to "manifesting psionic powers".
If anybody wants to play this concept, I will make a more customized one.