It should be possible, just a concept, not sure it works with this code, but you can modify the rest.
--- server
addCommandHandler("adminchat", function(player, _, ...)
for _,v in ipairs(getElementsByType("player")) do
if isObjectInACLGroup("user."..account,aclGetGroup("Staff")) then --- uses ACL to determine who is able use.
if (getElementData(v, "adminchat") == getElementData(player, "adminchat")) then
outputChatBox("#7D6608[Admin]#9A7D0A"..getPlayerName(player):gsub("#%x%x%x%x%x%x", "").."#7D6608: #FFFFFF"..table.concat({...}, " "):gsub("#%x%x%x%x%x%x", ""), v, 255, 255, 255, true);
end
end
end
end);
--- client
bindKey("u", "down", "chatbox", "adminchat");