:: A more realistic weapon equip animation. Instead of the weapon materializing out of thin air, when they are eqiupped in the inventory screen, swords should appear sheathed on the sides or back of a character, blasters holstered, lightsabers holstered, staffs strapped on the back, grenades on an ammo belt, and so on.
:: Varied lightsaber hilt colors and styles.
:: Of course, an all-new graphics, lighting and physics engine, preferrably borrowed rather than built from the ground up. Content, above all, is most important in RPG's, as is the time to create it.
:: Leave development to BioWare. Obsidian's efforts were superb, but KotOR belongs with BioWare. I know, this is wrong to post on an Obsidian forum. Forgive me.
:: More party member possibilites, possibly around 20 or so, making their cooperation restricted by alignment, sex and appearance. This would extremely increase replay value, since even more than one play-through as a LS Jedi wouldn't be the same.
:: More clothing and armor options, like changing different articles independantly (pants, jacket, shirt, shoes, gloves, headgear), rather than having one item for an entire set. Not to mention the inclusion of Jedi Force-friendly armor rather than just robes alone.
:: More in-depth character creation; body build, height, race, hair color, eye color, etc.
:: Even more lightsaber colors. Red, green, blue, yellow, silver and orange are the only crystal colors in the galaxy? What about white or extremely light grey? How about a black blade with a smokey, flowing glow; pure evil.
:: Dismemberment! This makes combat rewarding. After all, lightsabers can cut through anything--expect in KotOR.
:: A more fulfilling, in-depth romance side-story.
:: [Possibly] real-time space combat. I'm not sure how it would fit in with the D20 rules system, but it would be cool.
:: The ability to build and customize your own spacecraft. This goes hand-in-hand with the real-time space combat, since upgrades would enhance the performance of your craft.
:: Revan! Don't know what happened to him (or her), but a cameo would be a nice addition to the next installment.
:: The limited ability to attack anyone you meet, rather than being forced to be made into an imbecile and dismissed from an obviously lesser opponent. This happens too often in the game--and so often do I want revenge. And, I say limited since killing everyone leaves an environment lifeless and uninteresting.
That's all I can think of at the moment.