I don't think you're after multitexturing. Maybe I've misread the question. But are you asking about loading a single b3d file which contains several separate objects? Each of which requires a different texture?
If so, that's no problem, and you don't need to mess around with UV sets or multitexturing. Just parse through the children with FindChild/GetChild and apply textures to each. They will need to be separate objects within your modelling application in order to do this, but they probably already are.
If so, that's no problem, and you don't need to mess around with UV sets or multitexturing. Just parse through the children with FindChild/GetChild and apply textures to each. They will need to be separate objects within your modelling application in order to do this, but they probably already are.