So, after talking with Laughing a bit tonight, we came upon the quesiton of what happens when we need to alter vendor tables, as it involves modifying a roottemplate (compatability issue).
The game can handle modifications done to a level by seperate mods, so it looks like if you need to modify vendor tables, you are best off making your own vendor and placing them in town somewhere.
Is there a better solution than this? It gets the job done but then you have a town with 20 vendors if you have a lot of addons installed!