Remember, you can change the model in the division designer. It's just your enemy who won't see the amph model then, but once you put some battalions in a division you change the division model manually in the division designer.
Not exactly sure what you mean. Like, yes you can change models but only the type of brigades which make up most of your division. Like a mostly infantry division, you can pick between guy with Assault Rifle, guy with SMG, guy with bolt action rifle, and guy with old WW1 rifle. You can't exactly make the Infantry division model look like a tank or the artillery model.Since last DLC you can pick which 3D models are supposed to represent your units.