Anyone who read Alla's writeup on their visit to S-E's US headquarters should know that the idea of seeking on multiple jobs was mentioned. Maybe S-E will implement it, who knows? But in the meantime, I've been considering for a long time the possibility of having a global LFP channel much like other MMO games do, such as World of Warcraft. One chat channel useable by anyone in the game for finding parties or finding party members.
So, let's say you have a level 75 job but you want to XP a level 40 job - at current, you're stuck sitting around seeking for God knows how long until you get an invite or find enough to make your own party. What if you could be out farming on your 75 while still looking for a party for your level 40 job? The way to do this, of course, would be to advertise that you were seeking a party on the LFP channel, much in the same way that people regularly do through shouts, the difference being that it would be read by people who actually WANT to read it.
Also consider how often you build a party and are unable to find that one last member that would make it complete. A Paladin, or a Red Mage perhaps. You've asked every such job in the world, seeking or not, and none are available. There are many people out there who level multiple jobs simultaneously, myself included, and even while I'm seeking on, say, my Corsair, I wouldn't mind the chance to level up my White Mage. So an upcoming party could advertise on the LFP channel that they were seeking a level 46-48 Paladin or Ninja, and perhaps someone who was already seeking on a level 75 whatever, yet had a Paladin or Ninja that level range, would see it and decide to level that job instead.
This channel could also be used to find parties for BCNM, KSNM, Quests or Missions. Anything that involves finding members.
Now of course no such global channel exists, and likely will ever exist. But I've long been thinking of a viable alternative, one that I've been hoping someone would decide to make - but since none has been made, I have made it myself. The alternative is one single Linkshell, aptly called "LookingForParty", with a bright green pearl. I have attempted shouting about it in various zones but sadly, there is little room for explaning the real use of this Linkshell in a shout.
It's not a social or chatting LS, merely a hopeful means of making it easier, faster and less painful to find an XP party. And it cannot work without the support of a great many players. I hold the Shell, but I am not attempting to claim any form of leadership. All I want to do is get it started and give everyone in it pearlsacks so it can keep spreading, and so that anyone who wants it can easily get a pearl from just about anyone.
If you think this is a good idea and would like to help it reach fruition, find me in-game for a pearlsack.