If all you have left to do is the BMDB (battle_models) its not so bad. Make sure to make a copy of all original files before you edit them incase you mess something up. The easiest thing to do when you want to get rid of the silver surfer look is just copy and paste the textures from the original faction to the new faction:
So lets say you are scotland, take everything under england (red) and copy it to the part under scotland (blue). Its pretty easy if all your doing is changing units between factions, just tedious. That is the only way I know of to do it.
Also remember that when you are adding in factions under a unit you have to change the number above factions:
Any mistakes you make on this file will cause a CTD and the game wont be able to trace it (yea dumb I know) Thats why you always have a back up original file and make small changes at a time then test them in game.