There have been a few threads discussing how to make the game harder, longer etc, so here is my suggestion. We have a fantastic resource of MTW players who probably enjoy the same things about the game as us so lets use that and suggest challenges for each other. Then people can give feedback on which are most challenging / fun.
The challenges could use restricting certain units, self imposed rules etc etc
Heres one to get the ball rolling -
Italians, expert, early
Rules - no building any ships at all!
Challenge - win (60%) before the start of high.
Comments and further challenges greatly appreciated!