I know this a (very) old topic but I just wanted to point out that throughout the whole post the point was preparing for new, unannounced mobs that might have the ability to fly/dig. But you can never build a good enough fort if mobs just keep getting smarter and new mobs keep getting new abilities. It just isn't possible. The idea is good but if somebody tries to redo something like this (like buddy suggested above) to only include current mobs in your defense, 'cause otherwise the only good defense you could build in survival is a bedrock box with enough room for you and a wheat farm.
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ragnarock200: awesome, are those things with the creeper faces pistons or furnaces
Snowey1994: There dispensers