Now I think that this would be a really good idea to be able to make
custom wood signs like a sign post where we can either mouse over the
sign to see the message or click on the sign to see it.

And to be able to enter a custom message on the sign of so many
characters.

It would just give the game and a players city a bit more of a
customized feel.

As to what skill it would fit into which already exists in the game
I would say Woodworking.