A few months ago I was slowly working on creating a d20 Vana'diel game. Not exactly FFXI, but using elements from the game created in a fusion between Iron Heroes and DnD 3.5. I stopped mostly because I wanted to spend more time focusing on bg-wiki(also, I'm terrible at creating monsters stats). Since there has been a forum made, and it's probably going to be mostly empty, I thought I would share my notes on the postponed project. I'm only giving a simple look at the idea, so if it is hard to read / unorganized, I apologize. This is literally being written as I think to mention it(and I'm pretty tired).
Now the setting was Vana'diel but it wasn't the same exact world as FFXI. I'd add a few things (as vaguely as possible) to fill in the blanks. For example, I'm not quite sure if the Middle Lands are about the size of Florida, Europe, or Asia, but I grew/shrank them to about half the length of Europe(Qufim would be at Southern Sweden's height and Windurst's tip in Spain's most southern tip). Another thing I realize is that Vana'diel simply has to be smaller than Earth. To explain gravity, I used some ghetto science-fiction logic: Vana'diel's core is made of gold or adaman instead of Iron.
To flesh out other FFXI's details, the mythical hides and metals of Vana'diel are capable of doing things like stopping Iron bullets, allowing situations where a person armed with a musket being unable to defeat an Elvaan knight. On top of this I slapped on some typical anime-physics of Chi/Energy to explain jobs like MNK and SAM and the "weapon skill" system in general. Basically, adventurers are able to wield swords of gold with great finesse and able to survive a goblin bomb to the face because they become semi-metahuman.
One last thing I wanted to point out is on how I had Raise defined. Raise in this Vana'diel was basically an extremely potent, yet specific cure that would bring a person back to life. However, it would be very limited. Someone who couldn't be healed by a cure due to incurable wounds(beheaded, missing half their body, destroyed brain or heart, etc) would be hopeless and after a certain amount of the time the person simply couldn't be raised anymore. Finally, Raise, like resurrection spells in traditional tabletop RPGs, have great costs. Basically, while a WHM far surpasses a doctor in curing ability, they can't bring back the dead so easily.
As for the nations, I expanded on them greatly. The idea was that each Outpost was a considered a "Large Town" or "Small City"(in DnD terms, but I'm sure you understand them anyway) that had 1-2 neighboring hamlets(exception being Northlands and Qufim, which are much smaller). The capitals themselves are Metropolises with several suburban towns. Settlements were also added in areas where they would be likely to appear(Highlands for example). Selbina and Mhaura were made to be a Large City. Anyway, Outpost towns rotated control as there was an actual Conquest system. The towns would still be Windurstian/San d'orian/or Bastokian in culture and citizenship, but would only be able to trade to the nation that had the most influence in the area.
One last thing I'd like to touch on concerning the "fluff" was the geography. Like I mentioned before, I stretched Vana'diel quite a bit. Areas we are familiar with as being somewhat small would actually be miles and miles wide. And even with that, there would be blank spaces where one could actually put in their own made up areas. I was very conservative with this as SE could(and has with the new expansion) new areas at will. It's a nice little feature though. Anyway, for example, I had envisioned Crags to be almost mountains in size. What could be an unnamed set of trees in La Theine ingame would be turned into a full-on forest.
Concerning the "crunch", the system I was building for the game was certainly unique. It would use the basic feat/skill system in most d20 systems. However, it focused less on classes and more on feats. To mimic the many jobs and subjobs, I simply combined similar classes and let feats decide which is which. For example, Dragoon wouldn't be a class so much as a some generic named DD class with a set of feats that allowed them to Jump and have a Wyvern pet. This modeled played more after the type of Besieged/Campaign NPCs(or NMs) rather than traditional players. Spells would not be limited to the basic nukes and such. Things such as Shantotto's curses or complex teleportation spells would be available to PCs. Oh, and I even included food(only made through crystal synthesis) having a potent effect on people.
One major difference(from other games) would be that the level cap is only level 8(or 10, haven't decided) and from that point on players instead translate exp into a Merit-like system and boost up specific attributes or buy feats. This was to make the game simpler(as low level play > high level play imo) and more reliant on tactics, equipment, and specific actions(*cough*skillchains). This also meant players would hardly be able to reach the same power level as Dragons(aka, Fafnir or Tiamat). Such opponents could still be defeated with specific means that usually were tied closely to the story. I even toyed with the idea of an "alliance" event, where two or more groups teamed up to kill the highest caliber of opponents. But, I'm getting offtrack.
Weapon Skills worked under a "Token" system. Attacks, spells, and so on awarded temporary tokens. They could be traded in to perform weapon skills. I was considering extending it to more than just WSes and have certain job abilities(like an Elemental Seal type thing) to extend their use to all jobs. Weapons were not limited to the same lists of WSes that were present in the game. It worked more so that certain weapons could have one of a few elemental choices and a person choose which element and weapon combo they wanted to specialize in.
Skillchains work much the same as they do ingame and usually are very important for a most effective strategy. A usual balancing problem between mages and melee in tabletop RPGs is the way mages can perform such potent magic while melees are usually very limited if they wanted to catch up. WSes and SCs basically branch it together and additionally allow for the Magic Burst mechanic to appear.
I think I'm going to stop now.
XI Wiki

