Is your preview image a .tga, of dimensions 280x280, and bit-depth 24?
Are you changing the text directly in the Attribute Editor, or directly in the .ucs file?
If you are cloning to a new name AND location, you can rename to your heart's content. If you are cloning to the same name AND location, then you cannot rename afterwards.
Could you show the .abp file? Are you getting missing .rgm error boxes?
Also, great mod idea!
Fortress Europe has long planned to add the Finns (and Hungarians, Romanians, etc), but we are waiting until we can add visual and audial content (as well as new Factions).