MAR has already divided a state in half (only the eastern half of PA is included). I think that’s a good way to go, IMO. Teams often consider regionals outside of their state to be their “home regionals” because it’s closer for them. In another thread about districts, I used the example of South Jersey and Delaware teams attending the Philly regional instead of NJ because it was much closer for them. You see the same thing in other regions (someone pointed out earlier that panhandle teams mostly competed in nola).
Of course, this wouldn’t be as much of a problem if they allowed interdistrict play.