Actually, I'm not allowed to go with the Unisystem rules, or anything that doesn't fall under the Open Gaming License, which is just about everything except d20. I've actually been asked to put into my proposal a completely new rule system, which I think I'm going to base on an idea I had for a computer CYOA a while back (http://www.adventuregamestudio.co.uk/yabb/index.php?topic=23178.0)...