This mod already exists and has done for some time AFAIK.
The one age mod or all ages mod allows you to play with any nation of any age all together.
So you simply select all MA Nations minus MA Ermor and put LA Ermor in, I do it in SP all the time, as a impossible LA Ermor provides more of a challenge.
Unless of course Edi you plan on altering the units/leaders/mages of either/both MA/LA Ermor.
Edit
Just read Edi's last post
, yes I understand you are changing the nations so they are more thematic.
Good idea...
