Hey, guys, EMC is really cool, partly cuz we have "Feature" signs, which can be shops, [ teleport ] signs, [ message ] signs, and something else, that I forgot. . So why don't we make them redstone compatible? i.e. We could have signs, that when clicked/activated, send a redstone signal. This could make a shop sign, that when clicked, could trigger a message sign, that could say "thank you for buying 1 ___". i.e. We could also have a donation hopper, with a comparitor, that could trigger a message sign, that could say "thank you for your donation" i.e. Also, this could help with tp hubs, where the destination has a message sign, we could have the message sign at the tp hub, and than save resources.
Chest with comparator out the back hitting a block with a torch that goes into a dropper underneath the chest. Put as much items as you want in the dropper and one item in the chest. Shop sign on the chest for the price and the torch will flicker everytime someone buys something.
Referring to this, you can place a chest underneath teleport signs and the message will display on teleport, if that is what you are asking for.