Hello!
Background: We're playing with friends in hot-seat mode (8 people on one map) following this principle: the first player takes their turn, saves at the end of their turn, and sends the save to the next player. The next player loads the save when they're ready, clicks the "end turn" button (for the previous player), takes their turn, saves again, and sends it to the next player, and so on.
This approach is due to the inability to play online, as we are in different time zones (it's very difficult to synchronize 8 people for this).
As you can guess, in this game mode, there is no way to check if a player is actually paying attention to what the opponents are doing.
Suggestion: Could you add a mode to the game where each player (for example, when generating the map) could enter their own password, and then, at the beginning of each turn, the player would have to enter their password to make their turn, and when they click the "end turn" button, a save would be generated for the next player.
Regarding the substance of your suggestion, passwords do exist in the ND mode, but they are displayed in the saves, and if you send them to each other as in your example, these passwords seem to be irrelevant!