[Illuminated One]

While I would thematically like the ability to add new paths I like Jim think it is hard to implement.

Adding/changing a nation, spell, unit, item, magic site affects nothing but that nation, spell, unit, item, magic site.
Adding a new path requires all nations to have places where the gem income is stored and all units need some place to store their pathlevel, too.
And that is both in the UI and behind the curtains.
If those places have not already been reserved then old games probably would be incompatible with a version that has more paths.