Dang, I wish there was a Get_Planet_Conditions and a Get_Planet_Radiation, or even Get_Planet_Minerals and Radioactives... all of these could be argued to relate to the magnetic field which is tied to rotational speed. (Tilt could be tied to climate, temperature, organics and location.)
Well, good luck! My next idea is to put little effect clouds in orbit of protostars.
[edit] I suspect there is another problem with a single Gas_None, it is that they will be disproportionally represented in the quadrant... Unless the random selection isn't weighted against their appearance, 1 in 5 Gas planets will be that Gas None. I could be wrong about this... but when I tried the FQM beta GPT there were a lot of them in Mid-Life and Ancient Quadrants.