I can’t see how making a SP go a certain amount of innings has anything to do with the way this game has ever been played.
The bull pen strategy or whatever you wish to call it is only a direct result of pitchers going on the DL because every pitch can result in a home run and they’re injuring themselves trying to avoid that.
If they’re going have a rule about pitching a certain number of innings, they should add the 10 run mercy rule and be honest about the Mickey Mouse nature of these changes. Of course, I don’t know what their series of ifs, ands, or buts are that will adjudicate all these possible complications.
If they’re going to do anything, they should deaden the ball so pitchers are not throwing their arms out of whack and getting TJ surgery for fear of giving up a plethora of long balls.