This idea has also been mentioned to some extent in these older threads:
A small idea to better your heartlings
One issue that came up is keeping everything balanced, since the system only works on a (quite narrow) range of six–if you’re talking about body, faith, etc… A rare item might be a better way to go about it than a dedicated class or structure/workshop. However, I think this is something that needs to go to the Titans when they start getting added, or to an insanely-rare merchant that pretty much threatens to collapse your entire economy by buying just one of the things.