The current command-block chain that handles clearing out the build area only clears two(2) 32x32x32 area.
A more complex chain is required.
Also, the best method and command order would place water in the ocean, clear all the chunks in and around the build area, and then rebuild the build platform.
Currently, the Player has to manually switch out of Spectator mode to reset the game.
This is the one thing that feels out of character of the map and breaks immersion, in my mind. Requiring the player to manually switch modes can cause confusion or frustration if the player is unfamiliar with worlds with cheats enabled. It also might lead to confusion, causing the player to not realize they can still reset the game after the Timer reaches 0.
Expected behavior:
When the player reaches the Control Panel island they are automatically placed into Adventure mode, where they can reset the game or switch to creative to continue building.