So for my idea is something from wow itself (gothic the harvester) and does me remind me à bit of "art of defense" from command & conquer.
The idea is to have 2 seperate sides lined up next to eachother, 1 Side alliance other Side horde.
Each team has time to prepare themselves for The battle and when the time ends, waves of mobs Will spawm each time 1 sides kills mobs the other Side gets more mobs. Mobs Will get harder each wave. Each team needs to kill xx amount of MOB's between the timer and if they kill them in time they Will make it harder for other Side. That is the standard idea, maybe as soms extra there could be defense towers with Cannons or 3 lines of walls that the wave of mobs needs to get through or ways to give the other Side a hard time , there Will be ways to repair your walls, upgrade ur cannons extra buffs, the bg Will have 15 players on each Side with a rather short reviving time when died so battles wont go to fast there Will be à timer for around 15-20 mins or when The waves kill the last door to defend. There Will also be à mob timer that Will keep track of who/what team made the most kills.
Please give you're opinion about it and you're idea about it.