This sounds interesting, but it reminds me of other games. Therefore I do not like this mode for Eggwars, but let me explain why.
Let me start with the main premise of this whole mode. You want the games to almost work like Survival Games where there is a set amount of fighting time and then a death match. The problem is the whole point of Eggwars is that you have to destroy an egg to be able to kill off the players. With this mode, it would make eggs basically void. I am sorry, but this really changes the game as a whole and makes it into a different game that already exists.
In all honesty, this is like Survival Games with eggs. Also how would they get the gear and eggs in 20 minutes? It can take up to 10 minutes to get all the gear you may desire, but if the islands are being destroyed then the eggs are void as well as the shops. This would make gearing up a huge challenge and no one would go for eggs. People would just get the gear they need at the beginning and wait for the inevitable death match. I do not see this solving the campers until the death match starts, which just destroys the purpose of the original game.
if you read the islands will be start to decay after 20 minutes