Just had an idea. What if returning the Ring didn't give a cultural victory, but instead worked as a sort of Armageddon weapon. Like the destruction of the Ring for the Alliance destroys Barad-Dur and all non-human soldiers (orcs, trolls, goblins, etc.) in the enemy's forces. Or the return of the Ring for Mordor gives Sauron the ability to see the whole map, every unit, and gives free upgrades to all Mordor's forces to super powerful units, lowers unit production costs, etc. Make it so the game isn't over, but it's going to get more ... interesting. You could even make it so that it ends the war with Mordor, and makes diplomacy with the other civs possible. The alliances end and now jockeying among the remaining players becomes possible, whatever their old alliances were. In fact, that could make game play as the Shire, Elves, Dwarves and Bardings more interesting, since even if they don't get to be a major player in the war, they could still try to rise to prominence in the after-war world. Gondor-Arnor would be hugely powerful, but still fighting the other human nations, and the others could still fight and expand, etc.