Base of 15 + dodge score = AC if able to dodge, etc.
15 + dodge + active defense for when you're making an active defense.
I know it's not perfect, but I think it should work. Comments? Suggestions? Flames?
Also, if anyone has a good idea of what would be suitable DCs for various actions? In general, I can keep the D&D thing by raising DCs by 10, but people aren't going to be advancing in their skills nearly as quickly. Maybe increase by 5? 8?