For creating/manipulating/exporting meshes, it's important to have efficient access to the Pool*Arrays. It's not trivial, because they are locked to prevent multithreading issues. Godot-python would need to lock the array and get the raw pointer using array.read() to get the lock, reader.ptr() to get the raw data pointer (which can be turned into a python buffer, numpy array etc.), keeping the array.read() object around until done. Unlocking would have to be explicit in python since objects don't always get deleted until gc, something like a python-level reader.free() that would delete the underlying gdnative object.