Hi ekarabelas,
we are indeed developing a package to do this. It generates a smooth stl mesh from voxeldata and this stl geometry can be meshed by Netgen afterwards. The code is available at GitHub
github.com/ChrLackner/voxel2stl
Note, that this project is in a very early stage and has a lot of flaws still (as well as no documentation). But you are welcome to try it and contribute.
Feel free to contact me if you want more information or help on this project.
Best
Christopher