Curious if the idea of having an LS poster board in each city ever came across the dev's minds? Rather than having people shout in Ul'dah/Grid/LL chat about their linkshell, they can post it on a board, similar to FFXII's Marks. On the board, you can categorize what kind of LS/FC you're running (i.e. Social, Endgame, Static, HNM, etc) and allow a brief description of said LS/FC. If someone is interested in joining, there can be a send feature that allows the sackholders to invite this person.

Granted, I have no idea how Free Companies are going to work, perhaps if someone is interested in applying, there would be a "Send Application" function to the FC estate/HQ/whatever, kinda like a mailbox in other MMOs.

This is a really broad idea, and I'm posting at 5am, so forgive me if nothing is making sense. Feel free to mess around with this until a solid idea is formed.