I like this a lot. It's intuitive. It makes 18 expensive, but not ridiculously so. And it leaves open many, many stat options from hardcore (18, 18, 11, 10, 10, 8) to mixed (the pregen array or something more like 18, 15, 12, 12, 10, 8) to boringly well-rounded (14, 13, 13, 13, 13, 12)...