Adding Some Difficulty

[Imp]

For the real lunatics out there, you can make a game 70-80 turns and put the victory hexes along the extreme left and right rows of the map. Just playing long battles in general is difficult by itself. Not fun to realize on turn 6 of 79 that all your spotter planes are dead, and all your artillery is out of shells by round 14, etc

This would work to your advantage not the AIs. The converse is true less width benefits the AI as a rule. It remains more cohesive by point of contact as its not had time for fast units to run ahead.
Even defending the AI generally benefits from the map being smaller rather than larger for the force in question.
Big map for the force size gives you more avenues of approach & normally spreads the AI thin allowing you to easily have area superiority & pick off a few units at a time.