I think the best way of keeping interest throughout the game is the more imaginative "Glorious Achievements" from MTW and that's something I'd really loved to have seen in RTW and really hope is in M2TW.

Knowing you have the objectives to shape your strategy around, and not being forced to win by unrealistically conquering the whole of Europe, and then introducing new ones progressively through the game- the idea is in my eyes unbeatable and the way of turning the mid to late parts of the total war games.

Of course it seemed like the GAs in Medieval were sometimes rushed in- homelands only and that, but there were some crackers in there.