Hmm, I've been thinking of such a list for a while now, and here goes:
- New lightsaber animations (Give it a more movie-like feel, if possible)
- No wierd particle effects! )Like the flat red-looking rope that wound itself around your hands when doing a Master Flurry, what was that for? I hated that effect. Same with Critical and Power attack. And no particle effect on the wound/choke/kill force powers either, those effects ruined the fun of it for me)
- During lightsaber combat, no sparks from the lightsabers, only the big lightflashes should be kept. Sparks are for swords, not lightsabers.
- Include flashbacks to the Mandalorian Wars, but better ones than those in the cave in TSL on Korriban.
- Unique lightsaber hilts for all important Jedi, and a few unimportant too. And no dull ones either.
- More support for the modders community (That's a big thing for me, because I like to mess around with my games, even though I might not release anything)
- More interactive NPC's, that walk around talking to each other, maybe even brawl in the cantinas over a sabbacc match.
- More planets, both known and unknown. I would like to set foot on Coruscant, maybe tread inside the Jedi Temple and the Senate.
- Bring back a few old characters, depending on the timeframe.
- Create a flashback where you see Darth Nihilus be born on Malachor V, or something like that. Either way, give him a small appearance, even if it's only in a dream-like vision.
- Bring back my hero, Trask Ulgo, the most efficient and most interesting and well-developed NPC of all times! Even beating Kreia! I mean, seriously, his dialogues are the coolest out there, "To move the camera, move the mouse to either edge of the screen", nothing can beat that! He taught you everything he knew, and he fought against a Dark Jedi (Bandon), and probably died, but still. Bring him back for the tutorial (A flashback to the Endar Spire!).
- Re-use some known Sith Lord from the other two games, unless it is Kreia, but she should only have a short appearance as a Force Ghost.
- Umm... A few things people already have mentioned, plus my own "Do's"-list but the other way (Meaning that they cannot not do it).
That's my list.
Oh, and I'm very serious about that Trask Ulgo-part.