There is a modification that removes NotR: 
Gothic II Classic Mod  Description says it should work with the English version.  
 It's not 
exactly the same, but very similar. Haven't tried it myself.  
 EDIT: 
 According to the description, there are following differences between the "real" classic version, and this mod: 
 -) You can do the Novice quest in Chapter 2, which was not possible 
 -) several exploits and bugs were fixed 
 -) There are new ways to defeat the final boss (I'll keep this one vague, so not to spoil anyone) 
 -) What they kept from the add-on, is that it is harder to climb the city walls 
 -) There are also some visual effects retained from NotR, magic spells for example 
 -) They're not sure if there are differences between Classic and the Add-on regarding textures, music and the fighting AI of the monsters. If there are, they're also in this mod. 
 -) With 1.1 you now get 30% of the price with merchants, as it was in the original (in NotR it's only 15%) 
 -) They've also reimplemented the possibility to finish the game without joining a guild