One thing I would like about a KOTOR MMORPG is the chance to be a minor impact character in the storyline, and not some all-important hero who gets to decide the fate of the galaxy, like Revan, the Exile, Anakin, Luke, and others.
Another thing that would be necessary in a KOTOR III MMORPG is storyline and time advancement. The only time Star Wars: Galaxies had such was the Battle of Restuss (face it, KOTOR III the MMO will be constantly compared to Galaxies, just because they share two themes, "Star Wars" and "MMORPG"). Also, there should be nonrepeatable quests (sorry, only one person should successfully destroy that Trandoshan thug harassing the cantina patrons) and a bit of interdependency even in the need for storyline advancement.
.... and don't get me started on OOC names