The recent X-Com games by Firaxis have a advanced option setting called Second Wave. Its unlocked after completing the game, and offers players various options to increase/decrease specific aspects of the difficulty for the game.
I feel a gameplay setting like this would feel right at home for Total War titles aswell, helping those that are struggling/annoyed with certain aspects of the game. While at the same time offering a increased challenge and replay value for veterans.
Some examples could be:
- AI legendary lords level up every 5 turns.
- AI loses bonus resistance to attrition.
- AI loses bonus replenishment.
- AI can disband low tier units if high tier are available.
- AI buildings take 1 less turn to build.
- Minor Factions are whiped off the map only ruins remain.
- Elite units are capped (insert # max per army).