I like the idea of piggy backing, and would even take it a step farther, but based on the way pitcher salaries are directly tied to the traditional roles currently in place I can't see anybody trying to go against the status quo of pitcher usage. Now I know it seems hard to believe based on our bullpen's performance thus far, and even historically, but over the course of a full season relievers in MLB as a whole out pitch starters in terms of ERA. The primary reasons being that 1. relievers rarely if ever see a batter twice and B. back end rotation guys pitch a high volume of mediocre to terrible innings which eats into the numbers put up by the small handful of true ace level starters in the league at any given time. I think the ideal formula, especially for a NL team, would be to employ a 3x3 man rotation where each member of the triple piggy back is expected to go 2-3 innings based on how they are pitching. It also allows for pinch hitting early in the game if the game situation calls for it as you aren't trying to get one guy through 6-7 innings. This way you could theoretically A. Give up less runs over the course of a season by minimizing the number of times a pitcher sees a batter twice and 2. reduce injuries as innings are more evenly distributed throughout the 12 pitchers on the staff. The only organization I could see this even having a remote chance of happening would maybe be the Rockies given their park and history developing arms but it would require such an organization wide commitment that it is essentially a practical impossibility.