I have to say, I like the idea of having a '3rd' type of magic in my game. You can call it 'psionics', 'mind powers', 'astral bending' or whatever floats your boat. I've been working on a system of my own to define the abilities of what I'll call my Psychic class for Onn. Psychic powers aren't native to Onn, but rather the Astral Plane. A Psychic, instead of drawing on their Ethereal Field to produce effects, have either learned how to or natually tap the Astral Plane and draw power from it in order for their minds to affect reality around them.
Mechanically, it's no different than divine prayers or arcane magic, but the small bit of fluff on where it comes from can lead to some interesting role-playing for characters that are practicioners or knowledgable of its existance. Up til lately, I knew that I wanted to include the mind powers as a 3rd magic, but I wanted something that would either appeal or repulse players as well.
Implementation was the difficult thing. Using something similar to 'spell slots' would seem a bit too inorganic, while the point systems of games past and present make the player play a numbers game. I think I have a system now that divides powers into levels, much like spells, but has a check associated with it depending on the level of the character and level of the power, similar to Clerics Turning Undead. We'll see how well it functions soon.