As much as I'd be interested in making Custom-made maps myself for
storyline purposes (I'd FRAPS it and voice-act a fan-made adventure), I
think that's what someone got busted for once in-game.
That, and the /salute Warp-Jump-50-Feet-Ahead-And-Run-In-Mid-Air hack.
The only thing I could see this helping with is:
1. Avoiding aggro. I say that because let's say a monster starts chasing
you. The server, like most MMORPG servers, is essentially running an
instance of FFXI itself, just like you are. Except they have authority over
what they can do. With that in mind, they have the same normal map set
as you. But if you load a different map on your PC, one that they don't
have, then you run down a tunnel that's not on their map, the monster'll
get confused and de-aggro.
2. Reaching Coffers, Chests, and Target Points just out of reach. While
that might be useful (yet useless in Dynamis), I kinda feel that defeats the
whole purpose of adventuring in the first place.
3. Reaching new zones. Ever since I beat CoP, I was wondering how to
zone into that "Obelisk" area that's supposedly on the North end of Al'Taieu.
I think it's a bit impossible to reach on account of the "Red Holographic
Walls & Force Fields" blocking you A-La "Star Trek" or something. But
who knows, eh?
I'm more interested in custom map BUILDING than editing. I have a City
in mind I'd like to build, lol.