One thing that is nice for plotting in 3D with stereoEEG is to be able to plot ROIs. There is already a surfaces keyword argument in mne.viz.plot_alignment does something similar. We've just added the marching cubes implementation in #9484 so it would be as simple as passing an atlas in the subjects directory, locating the aseg file based on the atlas, running marching cubes which only takes a second at most and then plotting the surface.

A call could look like this:

mne.viz.plot_alignment(raw.info, atlas='desikan-killiany', rois=('hippocampus', 'putamen', 'caudate'))