batching and instancing basically.
As for batching, vvvv doesnt have native support for that, but you could do it already in your asset pipeline with external tools, basically combining geometry and write material Ids as vertex attributes, to save draw calls.
And for many objects with the same model instancing.
And for instancing, you just need the instancer node and use it in the shader, there is plenty example around.
And engine wise, a deffered engine helps a lot in larger scenes. Here the forward shaders quickly make problems if you dont do frustrum culling and visibility culling, and at least occlusion culling with visibility buffer for batched scenes is not publicly available in vvvv. But it can be done with DispatchIndirect and a ComputeShader that culls according to a screenspace visibility buffer (also would benefit from hierachical z for speed up).
I am working on these things but I am slow with it a bit.
Regarding your question if model loading can be made dynamically.
Usually with todays high end graphic cards you can also load very large scenes at init time. You realy just need to take care for a good culling and draw call management then it should be no problem.