FontForge has a "Merge fonts" command. It's scriptable in Python, though that command doesn't seem to be part of the API. It would probably not be hard to imple

FontForge has a "Merge fonts" command. It's scriptable in Python, though that command doesn't seem to be part of the API. It would probably not be hard to implement the same functionality simply adding glyphs in a loop... or to add a function to the Python API.