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