Last night, our group tried a 3-player variant where we played only on part of the map. Recall that the boards fold into three sections. We used the two western sections -- we did not use the East coast section. Any hex that fell even partly on the eastern "panel" was not used.
The cubes dictate the game, but there are some things that we thought needed a change. We never send anything out to the Southwest. There is only one red city in the two available sections. We thought we could solve both problems by making Shreveport a red city and adding one more cube to make it enticing for our group.
We discovered that there are lots of cards that don't get used if the east coast is not in the game. Only one major line is available (New Orleans to Minneapolis). No hotels in New York, Boston, or Charleston are available.
One the other hand, three players get pushed into a tight game. Our 3-player games usually start by one person taking the Northeast. The next person then agonizes on his decision: oppose the Northeastern player and give the game to the player building in the Midwest or build in the Midwest and force the last player to be the kingmaker. Our variant takes the Northeast out of the picture entirely.
We're still not sure how to make the southwest more inviting. One thought was to add more cubes to the red city, and possibly moving it to Dallas. Another idea to add interest was to add another major line or two to make up for the ones that don't appear (Kansas City-Louisville or Atlanta-Dallas?).
I think our 3-player game is interesting and worth trying again.