Domination of worlds by alliances and players who have already defeated the fortress.

If you have an idea that can actually work without punishing the players that play fair (and are large and have killed the centre) then I'm sure everyone would be glad to hear it.

There are many, many suggestions I've seen but all would punish the players that play fair too. The main problem, is that there is nothing in the game after the fortress has been killed. The world isn't reset, the players aren't transported to a new world - there is nothing. Until that is resolved then nothing can be done, in my view.