Realigning MLB is a nice pastime when I'm bored. When there's nothing else to do, and not enough mental energy to proactively start something of consequence, I'll often draw the outline of the US & start re-dividing baseball.
Here's a proposal of eight four-team divisions.
Assuming two new expansion teams, one on the east coast and the other on the west coast.
Div 1. Angels, Dodgers, Padres, Diamondbacks
Div 2. Mariners, Giants, A's, New West Coast Team (Las Vegas or Portland?)
Div 3. Cubs, White Sox, Cardinals, Royals
Div 4. Braves, Reds, Rays, Marlins
Div 5. Rangers, Astros, Rockies, New East Coast Team (Charlotte or Nashville?)
Div 6. Twins, Brewers, Guardians, Tigers
Div 7. Blue Jays, Red Sox, Yankees, Mets
Div 8. Orioles, Nationals, Phillies, Pirates
Did my best to respect time zones and minimize travel.
Also my intent to preserve existing rivalries, i. e. Cubs/Cardinals, Yankees/Red Sox, Guardians/Tigers, etc.
Hoping this would create new rivalries. The crosstown teams in New York, Chicago, and LA just seem too obvious. Also, I have to think that Giants/A's, Orioles/Nationals, and Royals/Cardinals could be good, along with potential in-state rivalries in Texas, Florida, and Pennsylvania.
Would have liked to get pairs like Dodgers/Giants, Reds/Guardians in the same division, but the geography is what it is.
The new team in Charlotte/Nashville gets hosed a bit, as they have to travel across 2 time zones to get to Colorado, but I think that's the only division that's not in two or less time zones. The placement of the Rockies is really one of the most difficult parts of realignment. This could be solved if the two expansion teams were in Portland and Las Vegas; with Las Vegas joining Colorado & the Texas teams, and Portland joining the Mariners, Giants, and A's.
Not too worried about preserving two leagues in this plan, especially since we're putting city-sharing teams in divisions together.
I would have liked to have kept Milwaukee with the Chicago teams, but again; the geography. Brewers lose the Cubs and Cardinals in this plan, but I don't think that's so bad. The Cubs and Cardinals are chiefly rivals with each other, and Milwaukee is a secondary rival to both those teams. There's a lot of history with the Twins, Tigers, and Cleveland; and Brewers fans could do very well re-learning to despise teams in other northern cities.