Understand that the new rulerships are not used by all astrologers. With Uranus, Neptune and Pluto they are the shadow of Saturn, Jupiter and Mars. Not all newly discovered planets will be used, and not all incorporated into astrology as planets, but more as fixed stars, or asteroids. The orphan planet you are referring to first is not in our galaxy, therefore, if it is to be used (doubtful but if), it would be probably go under fixed stars. But not all heavenly bodies are used. Example, astrology uses only about 1500 asteroids yet, there are thousands of asteroids.
This is a long and researched process. We don't sudden incorporate a planet. When Chiron, Sedna, and Eris were discovered, it took thousands upon thousands of charts to determine its nature. New ephemeris were calculated to them. And personally with Eris (the last discovery in this solar system), doubtful if many astrologer will used it much, as it orbit is so slow, almost like a fixed star. It is still being studied, and to my knowledge those who have been studying and researching this have thousands upon thousands of charts to watch the patterns.
As for the name of this orphan planet, astrologers do not name the planets, astronomers do. Usually the astronomer who discovers the planet or asteroid is given the right to name it.
Nothing is made up, astrology does have an order.