Baseball shouldn’t mess with on-game strategies like specialized relievers or employing the shift.
Just enforce the existing pace of play rules. These were built into the game but are too often ignored. If you do anything, limit the number of times a player can step out of the box during an at bat.
Also, stop the stupid “expanded roster” thing in September. Or at the very least, stop allowing (up to) all 40 players to dress and be available. Teams play for 5 months with 25 players and maybe 7 or 8 relievers, but for one month they are allowed a 12 man bullpen and 10 available bench players? Nothing drags a game along worse than 7 pitching changes in the last 3 innings. Stop that nonsense now. And if eliminated teams want to see their younger players perform, get them on the 25-man active roster somehow. Phantom DL trips? Flat out release certain non-QO pending free agents? There are options here.
And yes, Yes, YES to bringing the DH to the NL. Seriously that league needs to quit pretending it’s still 1968...