You should rather use a force enum of all human players who are playing than all 12 player slots. This would avoid redundant event generation and save on some code execution.
Only humans can type game messages. Even if AI could be brought to do this via triggers, it would be far better to execute the command actions directly.
Only humans that are playing can send chat messages. Not all 12 slots may contain humans and out of those not all of them may be playing (started without a full house or droppers).
Only in this case would a chat event binding system be useful to save game resources. Such a system should prety much be 1 function call though with the same parameters as the chat event but without a specified player slot.