Capture the flag, kill the leader, or another version of capture the flag where the flag is carried by 1 defender.
Con, try making it in a way so people can spam smoke grenades and steal the flag.
-Alliance A wants to attack Alliance B so Alliance A types in Alliance B's name into a search bar ( probably located in alliance activity tab)
-All members of Alliance B get a notice that reads: Alliance A has waged war on Alliance B prepare for war (Whatever Con likes to put)
-Timer sets for 24 hours (Timer is shown on Alliance A and B's alliance screen)
-After 24 hours all the members of Alliance A is shown on Alliance B's alliance screen and vice versa (Probably a button for this)
-All members of both alliances can attack anyone within their own level range.(lv range 1= 10-20,lv range 2= 21-30,lv range 3 =31-40,lv range 4 =41-50)
-During alliance wars no one can attack members of Alliance A or B except members of the enemy alliance
-Nothing can be looted
-All raiders and defenders suffer no injuries
-All defenders will be in the compound when raiders attack even if they are out. (This prevents DMU users from getting an upper hand by being able to send survivors out and look for resources to repair damaged buildings/traps)
-For every raider downed you will loose 1 point and for every defender killed you will gain 2 points (Depends on what Con thinks)
Thats it for now. Feel free to give me some suggestions.