Well, it's essentially for recruiting team members as I need them - while I don't foresee the need for a programmer to help me at this time (since this is a chance for me to learn how to at least script with Torque 2D, the engine I'm using), I will need an artist. Now, the artist I talked to already said a prototype of the game in question would do better to convince him to help me out, which is a reasonable proposal. So the concept paper is, I guess, sort of moot at this point in time, but I figure if I need some additional help I can show this concept paper to potential helpers to make sure they grasp what it is I'm trying to do.
Plus, it's good practice, at least. I learned something already by writing one and discovering it's not really a proper GDD.