@Everyone Ragecakin' about: ONLY the caravan quest (to my knowledge) will be company limited, and I highly doubt being able to do this single quest with your friends is going to discourage them from joining their particular company. I'm personally more worried about weapon availability. I play Gladiator and Pugilist (both guilds are in Uldah) but PUG GC weapons come from Gridania while GLA's are from Uldah. You can still do ALL the rest of the game's content with your multi-company friends.
If you want to relate this to XI, relate this to the outpost missions and garrisons. As a San'd'Orian I could not do outpost missions to outposts my Bastokan friend's nation owned. Also, I couldn't do lolGarrison with him and vise versa. It's not really much different. The caravan quest is tied to one particular nation, and calls to that specific nation's army to handle it. This quest will likely be the repeatable seal quest, which makes sense why it would be company-specific.
Most of the time they do fail, mostly because the nature of combat is stationary, against a single target. While escort missions request you fight on the move against multiple targets. This concept works "okay" in FPS because the player can quickly neutralize targets quickly, not so much in an MMO lol.
A few games I have played have circumvented this problem very well though. When they place the player ON the caravan having to defend the caravan (and themselves) works very well. A lot of times they will throw in a big gun or cannon for you to play with making it that much more exciting. Being able to not worry about the "chasing after the convoy" part of it and being able to focus specifically at the threats (who are also moving at YOU, not running FROM you after a convoy) and makes it much smoother and fun.
Examples of this:
Call of Duty 4 (last mission)
Red Faction: Guerrilla (multiple instances)
Dirge of Cerberus: FFVII (somewhere in the first few hours of the game you defend a wagon from wolves with a cannon)
Due to the nature of XIV I imagine we'll see the traditional face-to-keyboard convoy missions that will be severely frustrating for all classes other than ARC and mages lol. I think of the Bombard event and how annoying that was when you were a melee class and had no one to help you lol. Especially when the enemies are ranged themselves /rage