albhertglasz created something like what you are looking for: [mInicraft (work in progress))
I think he does it using Geoms rather then loading a model.
Also another person has created this smaller snippet:
[Minecraft-like chunk generator)
Again, using geoms. Not sure if its better performance rather then loading a model.
Anyway - maybe you could use copyTo to copy your initial node around, but that sounds a bit intensive. [need clarifications on how to propely copy a node and parent)
This thread might also be useful, in particular since its mentioned calling loadModel isn’t too bad since Panda caches it:
[block world)