DomIIIDevDiary of January:
Before Christmas we begun a remaking of themes that will
make things easier. Both changing stuff and modding at a later date. Each theme is now made as a separate nation. This makes it easy to add, remove and change nations. This also removes the need for a nation to exist in a given era. There was no Pythium before
the break from Ermor.
And I am quite sure that somewhere the ability to add Ulm's resource bonuses etc was mentioned. So, no hardcoding and more than enough empty slots. PDF, it seems your sacrifice was accepted.
There might still be restiction on the number of nations in one game, but new nations can be added freely. Or, that's what I think.