Another thing I don't like about your system is that you give too much credit in exchange for taking very low scores. The advantage of the "law of diminishing returns" approach (the more you invest in a particular stat, the less extra benefit you get from increasing that) is that its a disincentive for extreme stats, and therefore leads to a more normal (bell-like) distribution than a linear scale would. You keep this at the high end, but at the low end your system is backwards. I think it's an improvement to allow scores below 8, but I'd sooner have -1/2 per extra point drop, so that minimaxing really requires too much min for relatively little max.