I'm sure every crafter liked signing their best items in FFXI..
Who wouldn't like this feature to be added to FFXIV as well..? Well.. here's my idea..
Since in FFXIV there no longer is the ability to choose which crystals to use, there wouldn't be any special crystals for signing but.. why not adding a "Sign Item" option at the end of the synthesis along with "Finish" and "Touch Up"..? The command, just like "Touch Up", would be available only for equipment like weapons, armor and jewelry.. and it would require a certain amount of durability to consume..
If we want to add some difficulty to the process.. it could have a chance to fail displaying a message like "The attempt to sign the item has failed." or, in case of success, "Item successfully signed!"..
Tell me what do you think about it..