I think it is time that the American League ends this designated hitter experiment. This is coming from someone who grew up an AL fan.
1. Power hitters have been outed as PED users at a higher rate than non-power hitters. If they want to clean up the game, the DH should be eliminated. Making a player play a real position will reduce the number of positions available to immobile juiced up power hitters.
2. The fan base for baseball is so much more educated than the fan base of 50 years ago. Look at the advent of advanced statistics, spray charts and shifts. Baseball is now a thinking man's sport. The strategy is now debated on sports radio. People will now understand all of nuances to dealing with substitutions regarding a pitcher. These could new be points of conversation and debate across the league. That will ultimately keep baseball in the headlines.
3. It encourages teams to sign stupid deals for players which cripple franchises. Only AL teams have 10 year contracts for huge $ for power hitters. No well run NL team would ever try it.
4. With the advent of inter-league play it is just easier to have one system.
5. If they want the All Star Game to matter and decide home field advantage for the World Series, it would be easier to play with one set of rules.
6. Finally, it is very weird having a World Series alternate between sets of rules. At times a NL team is at a huge disadvantage because they do not pay the big money for a power hitter to sit on the bench for a majority of games.