The models don't all share the same model file format. There seem to be two different formats the "old" one used mainly in Prophecies, Factions and Nightfall and then the new ones used in EotN. The ones in EotN contains normal maps and aren't explicitly describing which texture goes with which set of UV coordinates. Another problem is figuring out which textures should be blended with alpha enabled.

Some work has already been done since the last release.