Same nation/age in same game?

[Edi]

You could get most of the things the same, but not quite all since all nation specials are not moddable and reanimation lists are fixed.

But if you were to move MA Ermor and Lanka to the same era, then replace one or the other with the same recruitment list so that they were functionally identical save for reanimation lists and national spells.

For natuions that do not have a lot of specialties, it is easier to do. The two nations just can't have the same name.