Did someone say knuckleballers?
I not only feel that we need to move toward a way to incorporate accurate pitch selections, but I think that the game should factor in the potential career impact of pitch types. For example, pitchers with the knuckleball as their primary pitch selection should have a different aging algorithm than those who rely primarily on the fastball.
As far as rendering the pitch selections goes, I bought a great book last year that is an encyclopedia of pitch selections for thousands of MLB pitchers throughout history. It is based on news accounts, scouting reports, interviews, and biographies. This kind of information should somehow be added to a Lahman database or similar resource for importing in historical play.