I like this idea and was thinking about it when I first started playing PS. Having this as one of the venues to gaining stats makes much more sense than using PPs and trias gained by doing something completely unrelated; ie. why I can max charisma by killing trepors and mining platinum, still seems strange to me. I guess I can see my character is paying for ettiquette lessons, but it should take time to improve and there should be evidence of me actually using that stat, instead of maxing it out with some simple clicks of the button and in less than a couple hours.
Example would be to train Endurance, then actually running a certain distance or be active for a while before it levels up, like skills. Each stat can be levelled in different ways so that it is more related to roleplaying. This is actually starting to sound like how Elder Scrolls does it, train Strength, then once you use a skill that is related to strength, like mining or heavy armor, then your Strength levels up. Quests should be part of this though, so if a NPC wants you to learn something or answer some questions, then when you accomplish it, it adds to your intelligence. But, also if you don't do quests, then you can train Intelligence by interacting with the community or learning new skills that are best related to intelligence. Hmm, I wonder if this copyrighted by the makers of Elder Scrolls. Everything can always be improved on though, except maybe chocolate cake.