I realize the game is designed for 2+ players, but does anyone have any ideas for Solo play?

Any house rules from previous incarnations of the game, etc.?

There was only one fan made that I knew for the original game. My son played it a few times. The objective was the basic scenario that the winner was the first to score at least 25 points and have sole control of the center. The opponent was an army completely made of Stalwarts for example, 7 in a 50-point army). That army would just march to the middle. Since the Stalwarts were very tough, this scenario could be very difficult to beat. I am not sure if something like this could be translated to the new version.