What might also be cool is having the war zone a replica of the whole classic world but take out most of the scripts that would cause lag, make the buildings inaccessible(like they're boarded up because of the war), make the whole map pk friendly. All guilds at war can access the war map which means that you might have to fight other guilds that may be in the war zone. Kill counters would be activated for any guild you are at war with, of course reach x amount of kills you win. Enemies have red indicators on map so you can find and hunt then down.

Adding this.

Have high profile buildings like castle, sards, battle arena etc accessible in 'war town'. Guilds can fight in them and over them which would add a cool aspect. The scripts to actually spar in battle arena are taken out and the scripts for castling are taken out, these buildings would just act as unique war grounds.

Section off the map into territories and guilds can plant their flag on territory markers to claim it. The flag planter would have to go untouched for 15 seconds to raise their guilds flag. Flags are obviously destroyable if another guild comes in and takes over the territory.