Anyway, capes should deffinately be add to the game, but this is not a f2p game where you buy cosmetic stuff. When they are add they will be crafted or loot drops.
I am not a fan of capes. But if they are to be introduced, they must be available for free through the gameplay. No additional cost on top of the subscription fee.
Only if they have proper physics. Given that they have terrible hair and tail physics, I don't see them improving anything for capes. They would probably look like a board floating on your back.
The more options the better. There have been capes in previous games, just not as a separate piece (Nightingale armor for example). And even if there hadn't, who cares? Its not like its a lore issue.