Questions about an idea for a magic system

[UristMcRandom]

First off, apologies if I've posted this in the wrong forum.

Originally I had this lengthy paragraph of background, but a minor crash has left me impatient to rewrite this, so you guys get the short version.

I have this idea for a magic system where so-called "Trancers" can manipulate the world by entering a lucid dream-state and interacting with objects in their dream, at the cost of vulnerability in the real world the entire time. Has this or something similar been done before? (It's one of those ideas where you feel like you're copying something, but you're not sure what it is.)

[Newwby]

The 'Dragon Age' series of games touched on something similar but didn't rely on being in a dream state to use magic. It sounds vaguely familiar, as if I've heard or read of something with a similar premise before. Why worry if you're copying something though? If you have an idea produce it and more likely than not your implementation of it will become unique in it's own fashion.

TVTropes has it's own page on types of magic (http://tvtropes.org/pmwiki/pmwiki.php/Main/FunctionalMagic) if you fancy going through all the examples to try and track down something similar (whether it be for purpose of inspiration or a worry you'll copy something).

[UristMcRandom]

Okay then, I'm going for it.

[Falcon X]

I'd study the idea of Astral Projection. It's best laid out in the Shadowrun RPG system.

In it, full magicians can project their minds onto the Astral Plane (Ethereal Plane or Shadow Plane for D&D). They leave their bodies behind which are vulnerable. In the Astral plane, they travel at the speed of thought, can spy on people and things, interact with spirits, manifest in ghostly forms, and other things.
It wouldn't be unreasonable to combine this with allowing casting in-between planes.
Truenaming, or something like it, is a very flavorful approach to that. I would create a class that is based on Truenamer, but buffed by a ton of other Astral abilities.