Good idea but I would anticipate any world with already built-in proprietary payment solutions (I don't know the ones you mentioned), but they might be relying on that to profit from users, so they will do everything possible to try to prohibit use of external cryptos inworld. So with that in mind, would probably be a good idea to let users define any identifiers, then it will be much more difficult for system owners to find user items they don't like.