I suggest that admins add in another game mode on the main menu next to survival multiplayer so when clans want to have war they can choose that game mode and it'll be a way better to verify which clan won the war
how it would work is:
When u click on the game mode you will be given options to make your clan official on the leaderboards if you win
there is a set time limit which can be changed if wanted to end the war if there are still people fighting
there is a set kill limit which ever clan reaches that kill limit the war ends and the clan who reached it will win
A prize (chose by the admins) the most valuable players on either clan will be rewarded even if the other clan lost to show gratitude the leader of the clan that won will be rewarded with coins (reward can be changed if wanted)
2 game mode options:
A) (just an example) 10vs10 players who die on either team will respawn into a box above the arena to watch the rest of the fight the team remaining wins
B)(Another example) 10vs10 respawn players who die can respawn the team who reach the kill limit or time limit and has the most kills wins the match
there's a leaderboard section to show how many wins a clan has and which clan is on a win streak