Redesigning the shout system is really the only way to go. As much as I would like a "out of character" chat, FFXI just isn't very chat friendly. Your sentences are already horribly limited and the lone chat box isn't winning any awards, and I don't feel like having to filter chat so a bunch of city folk doing nothing can piss and moan at each other aren't spamming my log. If they can combine Jeuno shouts it'll go a long ways in helping but even then it's at the mercy of people willing to move from the "cool" spot that is PJ right now. Also, as much as I hate to see it changed yet again, implement Jeuno tax. You can't really do it just for Port. People will just move to Lower or Upper or probably Ru'lude. At least then you knock out at least like 50-100 AFK bazaars for sure.
Finally, to put the nail in the coffin, Abyssea NPCs give off a 100 HP tick 10+ yalm poison aura if you stand by them for longer than a few minutes. Yeah, let's see people wait on top of the NPC for hours with that in effect making life a chore for everyone else. In before poison aura kills people down below at AH in PJ resulting in emergency maint for 2 hours.