I don't know about JK2, but I used to replace skins in Counterstrike all the time with some really good looking high-poly models that looked fantastic. CS skinners used to bundle up 'upgrades' with new player and weapon skins. Some of these packs even have new sounds and sprites for explosions, etc.
Of course, with CS, you only have 4 skins per team to choose from. I'm pretty happy with the variety in JK2's skins.
<System Lords> | OC-3
126.96.36.199:29070 - Saber only, increased saber damage, reduced blocking, custom map rotation and more to come.