If I understand correctly the player has 2 armors, and unequipping one of them switches it into the other. Have players with the first armor (call it Armor A) tagged with the scoreboard players tag command (let's say "usingarmorA"). Check whether the armor inventory slot is empty; if it is, /clear Armor A from the player's inventory and /give it Armor B. In the same tick, remove the "usingarmorA" tag and give it "usingarmorB" tag. Deactivate these lines of Command Blocks, and turn on another line which does the same thing but checks for Armor B.
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Upload your world to a file hosting service (mediafire, dropbox, etc.). Post the link to your file in a new thread and add the map description.
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If I understand correctly the player has 2 armors, and unequipping one of them switches it into the other. Have players with the first armor (call it Armor A) tagged with the scoreboard players tag command (let's say "usingarmorA"). Check whether the armor inventory slot is empty; if it is, /clear Armor A from the player's inventory and /give it Armor B. In the same tick, remove the "usingarmorA" tag and give it "usingarmorB" tag. Deactivate these lines of Command Blocks, and turn on another line which does the same thing but checks for Armor B.