This is why my longstanding idea to scatter all the teams across all the divisions, so that every division spans coast-to-coast, makes sense. We don't have this ongoing debate about teams being lopsided across time zones, don't have to debate whether someone has to be added in the East to balance someone being in the West, don't have to worry about moving someone from the Eastern Time Zone west / Central Time Zone east but other CTZ teams get stuck in the West, ... scatter them, you get none of that.
Most teams get a rival, you pair them up and they stay in the same division. You otherwise, make it so there's roughly the same number of teams East vs. West in a division. Then, if someone gets moved, no big deal - no one has to change divisions. Or, you make a swap(s) to re-balance travel for the respective divisions.
Yes, I know why it won't happen, but it would avoid so many complaints that have long existed and avoid a ton of these concerns re: expansion and relocation and where teams go.