En este post dicen:
The last known information given on custom UI that I can recall was that they would not allow it on release but would eventually allow them. To my knowledge, the lack of custom UI options never stops people from createing programs that bypass such things (FFXI had something like this that gave you tons of information that normally you would not see, but was made against the rules because it gave players an unfair advantage over others).
Traduciendo lo importante, que en la release no permitirán las UI's custom, pero que con el tiempo dejarían usarlas.
Espero que antes o después salga alguna un poco currada, porque la verdad es que la default es bastante lamentable, sobre todo lo de los grupos, que tiene tela lo mala y poco útil que es la ventana del grupo.