I don’t think Major League Baseball teams are in the business of pampering anyone. The improved strength and conditioning of players in today’s game has helped hitters more than pitchers. Pitchers have to throw with more velocity and movement on every pitch to succeed. Relievers are generally not as talented as starters; to throw really nasty stuff they have to expend a lot of effort on every pitch, and wear out quickly. Or they don’t have enough good pitches to make it a second time through the order. Or they aren’t effective in the righty-lefty matchup.

Relievers could probably throw more innings per year if they kept more regular schedules—not as regular as starters, but more regular than they have now. That would diminish the manager’s ability to use them situationally, but it might help them be more consistent and mean a team could get by with fewer relievers. I see where this idea might have merit.

I do see some potential snags, though. The first is finding pitchers that fit the bill. You only have so much money to spend on relievers, and pitchers with the stamina and depth of stuff to perform this role are likely perceived (perhaps misguidedly) as potential starters by some organization—maybe even your own. If these guys are moving in and out of the back spots of your rotation you’ll have a hard time establishing the consistency you need to make this work. Second, finding pitchers that will buy in. There’s not a general market for pitchers in this scheme, so these pitchers would be developing a skill set specialized to your team. They might not like what that means for their careers, and given how short a reliever’s typical tenure is, you can’t blame a guy for thinking that way. Third, dealing with game situations. Even if you avoid LOOGYs and have a deep ‘pen, you’ll have guys that are stronger than others. You want to be able to use your bullpen ace in the most critical situations (which sometimes are only a couple batters long) and lesser guys when the game isn’t close. The situations you’ll face aren’t predictable, so it’s hard to make the relievers’ use predictable. And I do think their appearances have to be somewhat regular in order for them to carry higher per-season inning loads.

That said… this is just speculation on my part. Only way to find out is if some manager is crazy enough to try it.