But what about a change in perspective. After one kills the fortress, the world expands and the outer edges are surrounded by forgotten bases.
Lets say for 10,000 player world, the lead alliance kills the fortress. After this occurs, the world expands by half its diameter. On the newly created space is a danger zone of lvl 60+ very special bases. These bases do respawn and come with upgraded units like the fortress.
Its the rest of the forgotten faction retaliating to an attack on the fortress! They also have twice the attack range of normal forgotten bases.
When left unchecked, a base spawns on its own after every hour per sector. They will slowly fill the world unless the players can slowly push them back and remove all the special lvl 60 bases.