I agree that it depends on what fabric you're using. with some long pile faux fur the chest ruff could look full enough on it's own. Or you may need to stuff the piece with some batting. Sounds like a cool cosplay.
Sometimes cosplay is like pie.
People who make pie are awesome.
People who buy pie are pretty cool, too.
If pie is delicious, I will compliment the person serving it to me.
If they made the pie, I will absolutely compliment them on having made it, too.