Zelanter

Fan of Luke, eh? Here's something for you :
https://www.dropbox.com/scl/fi/6rjjh6uu3js6gzo0zwozj/Luke-KOTOR.pk3?rlkey=qxwzxx18zfjj0ker1l0nh31ix&dl=0
Npc/Playermodel : Luke_KOTOR

To be honest, it took me longer to find those KOTOR robes than to create this kitbash. Unfortunately, they are not rigged very well; the hands are quite wonky. If you or someone else could find a better model, I would be willing to remake this to eliminate that problem.

Here you go.
https://www.dropbox.com/s/ql2cip1fvel6zk8/Young Master Luke.pk3?dl=0
Npc/Playermodel - luke_ym
I made him in quite a hurry without extensive testing, so let me know if there are any issues and I'll correct them.

Hello there,
I’m not an expert by any means on this matter, so I can't guarantee you that this is the only solution.
The animations for models in this game are tied up to "_humanoid" folder files localized in the base\"assets1.pk3".
The mods that include custom animations for characters use their own animation folder to which they assign their models. So to change animations of one specific model you'd have to do something which is explained in this tutorial :    (Fun fact : Tompa9 who asked this question in 2017 is now one of the main creators for MD 2 which you've mentioned.)
 So you can't change animation for model only with a command etc. It's a more complicated process that needs to be done in model editing software.  
 
Easier way to replace the animations is to create your very own "_humanoid" mod. The drawback of this is that every model/npc will also use those animations.
So lets say that you want vanilla models/npcs to use a modded animations. You need to download a playermodel mod that comes with unique animations of your liking.
Open the .pk3 file of this mod with WinRAR, go to models/players. There should be the custom animations folder named for example "_humanoid_anakin". all you have to do is to extract the _humanoid.gla and animation.cfg files. On the desktop create a folder called "models", in it create folder "players" and in that folder create another called "_humanoid" and put those files you've extracted in it.
The path should look like this: models/players/_humanoid/_humanoid.gla + animation.cfg.
Now dowload PakScape : 
Open it, click "file"->"new", drag your "models" folder into the blank white space, and save it as a .pk3 file.
And that's it, your very own animation mod!
As for the stances, apart from the modified double saber stance that you've mentioned, there are no new stances in MD 2 ( atleast to my knowledge )
You probably didn't knew that in JA there are two hidden stances used by bosses. They're respectively named: "desann" and "tavion".
Basically it's the one-handed strong ( purple in MD2 ) and one-handed fast ( light blue in MD2 ). To use them in vanilla you need to type in console "setsaberstyle desann" or "setsaberstyle tavion".
To quickly change to them without having to type in those commands, just bind them to any spare keys on your keyboard. For example I use "u" for tavion style and "p" for desann's
To bind them, type in console "bind u setsaberstyle tavion" or "bind p setsaberstyle desann".
I hope that will help you 😄.