How dare you challenge the might of Jupiter! It weighs 320 times the mass of Earth -- even if those 100,000 trojan asteroids weighed as much as its minor moons (which they don't, they are 0.0001 Earth masses according to wikipedia), it would still dominate its gravitational field by several (9) orders of magnitude.
Compare that to Pluto: Charon already weighs 10% of Plutos mass. The center of rotation in that system is not even inside Pluto.
Also, there are other criteria that apply: a planet has to be spherical due to gravitation (there is a more technical definition). Is that the case for Pluto?
Finally, you can not have 9 planets anymore. You can choose between 8 planets and 13 planets, the latter group growing every year.