Supposed you have figured how to switch units around, create new generals and even new name for the new units, I think you can do this:
Go into the 'unit_models' folder and check the 'battle_models.modeldb'.
It seems not possible to edit, but just open it up with Notepad or any word editing tool.
The name of the models of the Swan Knights, the unit you are editing, is just 'swan_knights' - Ctrl-F and search it.
Now you have the lines out, you can see something like this:
Code:
....
6 sicily
72 unit_models/_Units/EN_Lmail_Hmail/textures/en_wmail_wmail_poland.texture
72 unit_models/_Units/EN_Lmail_Hmail/textures/en_wmail_wmail_normal.texture
43 unit_sprites/sicily_swan_knights_sprite.spr
4 merc
72 unit_models/_Units/EN_Lmail_Hmail/textures/en_wmail_wmail_poland.texture
...
You are playing as Silvan Elves- it's represented in game codes with 'mongol'.
Copy the lines starting from '6 sicily' up to the last line before '4 mercs'.
Replace 'sicily' with 'mongol' in the new lines.
Now you should have this:
Code:
6 sicily
72 unit_models/_Units/EN_Lmail_Hmail/textures/en_wmail_wmail_poland.texture
72 unit_models/_Units/EN_Lmail_Hmail/textures/en_wmail_wmail_normal.texture
43 unit_sprites/sicily_swan_knights_sprite.spr
6 mongol
72 unit_models/_Units/EN_Lmail_Hmail/textures/en_wmail_wmail_poland.texture
72 unit_models/_Units/EN_Lmail_Hmail/textures/en_wmail_wmail_normal.texture
43 unit_sprites/sicily_swan_knights_sprite.spr
4 merc
72 unit_models/_Units/EN_Lmail_Hmail/textures/en_wmail_wmail_poland.texture
.....
And so it's finished.
After you get that done, why don't you try also switch the battle model for your general?
You can have a special model like Arnorian armour for you 'Man-ish' general among your Elves.
Same veins with the above change, just that it's not save compatible sadly.